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Storm Water Management Plan For Priority Projects

(Major SWMP) The Major Stormwater Management Plan (Major SWMP) must be completed in its entirety and accompany applications to the County for a permit or approval associated with certain types of development projects. To determine whether your project is required to submit a Major or Minor SWMP, please reference the County’s Stormwater Intake Form for Development Projects. Project Name: Permit Number (Land Development Projects):

Work Authorization Number (CIP only): Applicant: Applicant’s Address: Plan Prepare By (Leave blank if same as applicant):

Date: Revision Date (If applicable): The County of San Diego Watershed Protection, Storm Water Management, and Discharge Control Ordinance (WPO) (Ordinance No. 9926) requires all applications for a permit or approval associated with a Land Disturbance Activity to be accompanied by a Storm Water Management Plan (SWMP) (section 67.806.b). The purpose of the SWMP is to describe how the project will minimize the short and long-term impacts on receiving water quality. Projects that meet the criteria for a priority development project are required to prepare a Major SWMP. Since the SWMP is a living document, revisions may be necessary during various stages of approval by the County. Please provide the approval information requested below.

Does the SWMP need revisions? Project Stages YES NO

If YES, Provide Revision Date

Instructions for a Major SWMP can be downloaded at http://www.sdcounty.ca.gov/dpw/watersheds/susmp/susmp.html Completion of the following checklists and attachments will fulfill the requirements of a Major SWMP for the project listed above.

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PROJECT DESCRIPTION Please provide a brief description of the project in the following box. Please include:

• Project Location • Project Description • Physical Features (Topography) • Surrounding Land Use • Proposed Project Land Use • Location of dry weather flows (year-round flows in streams, or creeks) within

project limits, if applicable.

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PRIORITY DEVELOPMENT PROJECT DETERMINATION Please check the box that best describes the project. Does the project meet one of the following criteria? Table 1

PRIORITY DEVELOPMENT PROJECT YES NO Redevelopment that creates or adds at least 5,000 net square feet of additional impervious surface area and falls under one of the criteria listed below.

Residential development of more than 10 units. Commercial developments with a land area for development of greater than 1 acre.

Heavy industrial development with a land area for development of greater than 1 acre.

Automotive repair shop(s). Restaurants, where the land area for development is greater than 5,000 square feet.

Hillside development, in an area with known erosive soil conditions, where there will be grading on any natural slope that is twenty-five percent or greater, if the development creates 5,000 square feet or more of impervious surface.

Environmentally Sensitive Areas (ESA): All development located within or directly adjacent to or discharging directly to an ESA (where discharges from the development or redevelopment will enter receiving waters within the ESA), which either creates 2,500 square feet of impervious surface on a proposed project site or increases the area of imperviousness of a proposed project site to 10% or more of its naturally occurring condition. “Directly adjacent” means situated within 200 feet of the ESA. “Discharging directly to” means outflow from a drainage conveyance system that is composed entirely of flows from the subject development or redevelopment site, and not commingled with flows from adjacent lands.

Parking Lots 5,000 square feet or more or with 15 parking spaces or more and potentially exposed to urban runoff.

Streets, roads, highways, and freeways which would create a new paved surface that is 5,000 square feet or greater.

Retail Gasoline Outlets (RGO) that meet the following criteria: (a) 5,000 square feet or more or (b) a projected Average Daily Traffic (ADT) of 100 or more vehicles per day.

Limited Exclusion: Trenching and resurfacing work associated with utility projects are not considered Priority Development Projects. Parking lots, buildings and other structures associated with utility projects are subject to the WPO requirements if one or more of the criteria above are met. If you answered NO to all the questions, then STOP. Please complete a Minor SWMP for your project. If you answered YES to any of the questions, please continue.

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HYDROMODIFICATION DETERMINATION The following questions provide a guide to collecting information relevant to hydromodification management issues. Table 2 QUESTIONS YES NO Information 1. Will the proposed project disturb 50 or

more acres of land? (Including all phases of development)

If YES, continue to 2. If NO, go to 6.

2. Would the project site discharge directly into channels that are concrete-lined or significantly hardened such as with rip-rap, sackcrete, etc, downstream to their outfall into bays or the ocean?

If NO, continue to 3. If YES, go to 6.

3. Would the project site discharge directly into underground storm drains discharging directly to bays or the ocean?

If NO, continue to 4. If YES, go to 6.

4. Would the project site discharge directly to a channel (lined or un-lined) and the combined impervious surfaces downstream from the project site to discharge at the ocean or bay are 70% or greater?

If NO, continue to 5. If YES, go to 6.

5. Project is required to manage hydromodification impacts.

Hydromodification Management Required as described in Section 67.812 b(4) of the WPO.

6. Project is not required to manage hydromodification impacts.

Hydromodification Exempt. Keep on file.

An exemption is potentially available for projects that are required (No. 5. in Table 2 above) to manage hydromodification impacts: The project proponent may conduct an independent geomorphic study to determine the project’s full hydromodification impact. The study must incorporate sediment transport modeling across the range of geomorphically-significant flows and demonstrate to the County’s satisfaction that the project flows and sediment reductions will not detrimentally affect the receiving water to qualify for the exemption.

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STORMWATER QUALITY DETERMINATION The following questions provide a guide to collecting information relevant to project stormwater quality issues. Please provide the following information in a printed report accompanying this form. Table 3 QUESTIONS COMPLETED NA 1. Describe the topography of the project area. 2. Describe the local land use within the project area and

adjacent areas.

3. Evaluate the presence of dry weather flow. 4. Determine the receiving waters that may be affected by the

project throughout all phases of development through completion (i.e., construction, long-term maintenance and operation).

5. For the project limits, list the 303(d) impaired receiving water bodies and their constituents of concern.

6. Determine if there are any High Risk Areas (which is defined by the presence of municipal or domestic water supply reservoirs or groundwater percolation facilities) within the project limits.

7. Determine the Regional Board special requirements, including TMDLs, effluent limits, etc.

8. Determine the general climate of the project area. Identify annual rainfall and rainfall intensity curves.

9. Determine the soil classification, permeability, erodibility, and depth to groundwater for Treatment BMP consideration.

10. Determine contaminated or hazardous soils within the project area.

11. Determine if this project is within the environmentally sensitive areas as defined on the maps in Appendix A of the County of San Diego Standard Urban Storm Water Mitigation Plan for Land Development and Public Improvement Projects.

12. Determine if this is an emergency project.

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WATERSHED Please check the watershed(s) for the project.

San Juan 901 Santa Margarita 902 San Luis Rey 903 Carlsbad 904 San Dieguito 905 Penasquitos 906 San Diego 907 Sweetwater 909 Otay 910 Tijuana 911 Whitewater 719 Clark 720 West Salton 721 Anza Borrego 722 Imperial 723

Please provide the hydrologic sub-area and number(s)

Number Name

Please provide the beneficial uses for Inland Surface Waters and Ground Waters. Beneficial Uses can be obtained from the Water Quality Control Plan for the San Diego Basin, which is available at the Regional Board office or at http://www.waterboards.ca.gov/sandiego/water_issues/programs/basin_plan/index.shtml

SURFACE WATERS

Hydrologic Unit Basin Number

MU

N

AG

R

IND

PRO

C

GW

R

FRES

H

POW

REC

1

REC

2

BIO

L

WA

RM

CO

LD

WIL

D

RA

RE

SPW

N

Inland Surface Waters

Ground Waters

* Excepted from Municipal X Existing Beneficial Use 0 Potential Beneficial Use

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POLLUTANTS OF CONCERN Using Table 4, identify pollutants that are anticipated to be generated from the proposed priority project categories. Pollutants associated with any hazardous material sites that have been remediated or are not threatened by the proposed project are not considered a pollutant of concern. Table 4. Anticipated and Potential Pollutants Generated by Land Use Type

Note: If other monitoring data that is relevant to the project is available. Please include as Attachment C.

General Pollutant Categories PDP

Categories Sediments Nutrients Heavy Metals

Organic Compounds

Trash & Debris

Oxygen Demanding Substances

Oil & Grease

Bacteria &

Viruses Pesticides

Detached Residential

Development X X X X X X X

Attached Residential

Development X X X P(1) P(2) P X

Commercial Development 1 acre or greater

P(1) P(1) P(2) X P(5) X P(3) P(5)

Heavy industry /industrial

development

X X X X X X

Automotive Repair Shops X X(4)(5) X X

Restaurants X X X X Hillside

Development >5,000 ft2

X X X X X X

Parking Lots P(1) P(1) X X P(1) X P(1) Retail Gasoline

Outlets X X X X X

Streets, Highways & Freeways X P(1) X X(4) X P(5) X

X = anticipated P = potential (1) A potential pollutant if landscaping exists on-site. (2) A potential pollutant if the project includes uncovered parking areas. (3) A potential pollutant if land use involves food or animal waste products. (4) Including petroleum hydrocarbons. (5) Including solvents.

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CONSTRUCTION BMPs Please check the construction BMPs that may be implemented during construction of the project. The applicant will be responsible for the placement and maintenance of the BMPs incorporated into the final project design.

Silt Fence Desilting Basin

Fiber Rolls Gravel Bag Berm

Street Sweeping and Vacuuming Sandbag Barrier

Storm Drain Inlet Protection Material Delivery and Storage

Stockpile Management Spill Prevention and Control

Solid Waste Management Concrete Waste Management

Stabilized Construction Entrance/Exit Water Conservation Practices

Dewatering Operations Paving and Grinding Operations

Vehicle and Equipment Maintenance

Any minor slopes created incidental to construction and not subject to a major or minor grading permit shall be protected by covering with plastic or tarp prior to a rain event, and shall have vegetative cover reestablished within 180 days of completion of the slope and prior to final building approval.

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EXCEPTIONAL THREAT TO WATER QUALITY DETERMINATION Complete the checklist below to determine if a proposed project will pose an “exceptional threat to water quality,” and therefore require Advanced Treatment Best Management Practices. Table 5

No. CRITERIA YES NO INFORMATION1. Is all or part of the proposed project site within 200 feet of waters

named on the Clean Water Act (CWA) Section 303(d) list of Water Quality Limited Segments as impaired for sedimentation and/or turbidity? Current 303d list may be obtained from the following site: http://www.swrcb.ca.gov/tmdl/docs/303dlists2006/approved/r9_06_303d_reqtmdls.pdf

If YES, continue to 2. If NO, go to 5.

2. Will the project disturb more than 5 acres, including all phases of the development?

If YES, continue to 3. If NO, go to 5.

3. Will the project disturb slopes that are steeper than 4:1 (horizontal: vertical) with at least 10 feet of relief, and that drain toward the 303(d) listed receiving water for sedimentation and/or turbidity?

If YES, continue to 4. If NO, go to 5.

4. Will the project disturb soils with a predominance of USDA-NRCS Erosion factors kf greater than or equal to 0.4?

If YES, continue to 6. If NO, go to 5.

5. Project is not required to use Advanced Treatment BMPs. Document for Project Files by referencing this checklist.

6. Project poses an “exceptional threat to water quality” and is required to use Advanced Treatment BMPs.

Advanced Treatment BMPs must be consistent with WPO section 67.811(b)(20)(D) performance criteria

Exemption potentially available for projects that require advanced treatment: Project proponent may perform a Revised Universal Soil Loss Equation, Version 2 (RUSLE 2), Modified Universal Soil Loss Equation (MUSLE), or similar analysis that shows to the County official’s satisfaction that advanced treatment is not required Now that the need for treatment BMPs has been determined, other information is needed to complete the SWMP.

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SITE DESIGN To minimize stormwater impacts, site design measures must be addressed. The following checklist provides options for avoiding or reducing potential impacts during project planning. If YES is checked, it is assumed that the measure was used for this project. Table 6 OPTIONS YES NO N/A 1. Has the project been located and road improvements aligned

to avoid or minimize impacts to receiving waters or to increase the preservation of critical (or problematic) areas such as floodplains, steep slopes, wetlands, and areas with erosive or unstable soil conditions?

2. Is the project designed to minimize impervious footprint? 3. Is the project conserving natural areas where feasible? 4. Where landscape is proposed, are rooftops, impervious

sidewalks, walkways, trails and patios be drained into adjacent landscaping?

5. For roadway projects, are structures and bridges be designed or located to reduce work in live streams and minimize construction impacts?

6. Can any of the following methods be utilized to minimize erosion from slopes:

6.a. Disturbing existing slopes only when necessary? 6.b. Minimize cut and fill areas to reduce slope lengths? 6.c. Incorporating retaining walls to reduce steepness of

slopes or to shorten slopes?

6.d. Providing benches or terraces on high cut and fill slopes to reduce concentration of flows?

6.e. Rounding and shaping slopes to reduce concentrated flow?

6.f. Collecting concentrated flows in stabilized drains and channels?

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LOW IMPACT DEVELOPMENT (LID) Each numbered item below is a LID requirement of the WPO. Please check the box(s) under each number that best describes the Low Impact Development BMP(s) selected for this project. Table 7 1. Conserve natural Areas, Soils, and Vegetation-County LID Handbook 2.2.1

Preserve well draining soils (Type A or B) Preserve Significant Trees Other. Description:

1. Not feasible. State Reason:

2. Minimize Disturbance to Natural Drainages-County LID Handbook 2.2.2 Set-back development envelope from drainages

� Restrict heavy construction equipment access to planned green/open space areas

Other. Description:

2. Not feasible. State Reason:

3. Minimize and Disconnect Impervious Surfaces (see 5) -County LID Handbook 2.2.3 Clustered Lot Design Items checked in 5? Other. Description:

3. Not feasible. State Reason:

4. Minimize Soil Compaction-County LID Handbook 2.2.4 � Restrict heavy construction equipment access to planned green/open space areas

Re-till soils compacted by construction vehicles/equipment � Collect & re-use upper soil layers of development site containing organic materials

Other. Description:

4. Not feasible. State Reason:

5. Drain Runoff from Impervious Surfaces to Pervious Areas-County LID Handbook 2.2.5

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LID Street & Road Design Curb-cuts to landscaping Rural Swales Concave Median Cul-de-sac Landscaping Design Other. Description:

LID Parking Lot Design Permeable Pavements Curb-cuts to landscaping Other. Description:

LID Driveway, Sidewalk, Bike-path Design Permeable Pavements Pitch pavements toward landscaping Other. Description:

LID Building Design Cisterns & Rain Barrels Downspout to swale Vegetated Roofs Other. Description:

LID Landscaping Design Soil Amendments Reuse of Native Soils Smart Irrigation Systems Street Trees Other. Description:

5. Not feasible. State Reason:

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CHANNELS & DRAINAGES Complete the following checklist to determine if the project includes work in channels. Table 8 No. CRITERIA YES NO N/A COMMENTS 1. Will the project include work in channels? If YES go to 2

If NO go to 13. 2. Will the project increase velocity or

volume of downstream flow? If YES go to 6.

3. Will the project discharge to unlined channels?

If YES go to. 6.

4. Will the project increase potential sediment load of downstream flow?

If YES go to 6.

5. Will the project encroach, cross, realign, or cause other hydraulic changes to a stream that may affect downstream channel stability?

If YES go to 8.

6. Review channel lining materials and design for stream bank erosion.

Continue to 7.

7. Consider channel erosion control measures within the project limits as well as downstream. Consider scour velocity.

Continue to 8.

8. Include, where appropriate, energy dissipation devices at culverts.

Continue to 9.

9. Ensure all transitions between culvert outlets/headwalls/wingwalls and channels are smooth to reduce turbulence and scour.

Continue to 10.

10. Include, if appropriate, detention facilities to reduce peak discharges.

Continue to 11.

11.

“Hardening“ natural downstream areas to prevent erosion is not an acceptable technique for protecting channel slopes, unless pre-development conditions are determined to be so erosive that hardening would be required even in the absence of the proposed development.

Continue to 12.

12. Provide other design principles that are comparable and equally effective.

Continue to 13.

13. End

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SOURCE CONTROL Please complete the following checklist for Source Control BMPs. If the BMP is not applicable for this project, then check N/A only at the main category. Table 9

BMP YES NO N/A1. Provide Storm Drain System Stenciling and Signage 1.a. All storm drain inlets and catch basins within the project area

shall have a stencil or tile placed with prohibitive language (such as: “NO DUMPING – DRAINS TO ________”) and/or graphical icons to discourage illegal dumping.

1.b. Signs and prohibitive language and/or graphical icons, which prohibit illegal dumping, must be posted at public access points along channels and creeks within the project area.

2. Design Outdoors Material Storage Areas to Reduce Pollution Introduction

2.a. This is a detached single-family residential project. Therefore, personal storage areas are exempt from this requirement.

2.b. Hazardous materials with the potential to contaminate urban runoff shall either be: (1) placed in an enclosure such as, but not limited to, a cabinet, shed, or similar structure that prevents contact with runoff or spillage to the storm water conveyance system; or (2) protected by secondary containment structures such as berms, dikes, or curbs.

2.c. The storage area shall be paved and sufficiently impervious to contain leaks and spills.

2.d. The storage area shall have a roof or awning to minimize direct precipitation within the secondary containment area.

3. Design Trash Storage Areas to Reduce Pollution Introduction 3.a. Paved with an impervious surface, designed not to allow run-on

from adjoining areas, screened or walled to prevent off-site transport of trash; or,

3.b. Provide attached lids on all trash containers that exclude rain, or roof or awning to minimize direct precipitation.

4. Use Efficient Irrigation Systems & Landscape Design The following methods to reduce excessive irrigation runoff shall be

considered, and incorporated and implemented where determined applicable and feasible.

4.a. Employing rain shutoff devices to prevent irrigation after precipitation.

4.b. Designing irrigation systems to each landscape area’s specific water requirements.

4.c. Using flow reducers or shutoff valves triggered by a pressure drop to control water loss in the event of broken sprinkler heads or lines.

4.d. Employing other comparable, equally effective, methods to reduce irrigation water runoff.

5. Private Roads

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BMP YES NO N/A The design of private roadway drainage shall use at least one of the

following

5.a. Rural swale system: street sheet flows to vegetated swale or gravel shoulder, curbs at street corners, culverts under driveways and street crossings.

5.b. Urban curb/swale system: street slopes to curb, periodic swale inlets drain to vegetated swale/biofilter.

5.c. Dual drainage system: First flush captured in street catch basins and discharged to adjacent vegetated swale or gravel shoulder, high flows connect directly to storm water conveyance system.

5.d. Other methods that are comparable and equally effective within the project.

6. Residential Driveways & Guest Parking The design of driveways and private residential parking areas shall use

one at least of the following features.

6.a. Design driveways with shared access, flared (single lane at street) or wheelstrips (paving only under tires); or, drain into landscaping prior to discharging to the storm water conveyance system.

6.b. Uncovered temporary or guest parking on private residential lots may be: paved with a permeable surface; or, designed to drain into landscaping prior to discharging to the storm water conveyance system.

6.c. Other features which are comparable and equally effective. 7. Dock Areas Loading/unloading dock areas shall include the following. 7.a. Cover loading dock areas, or design drainage to preclude urban

run-on and runoff.

7.b. Direct connections to storm drains from depressed loading docks (truck wells) are prohibited.

7.c. Other features which are comparable and equally effective. 8. Maintenance Bays Maintenance bays shall include the following. 8.a. Repair/maintenance bays shall be indoors; or, designed to

preclude urban run-on and runoff.

8.b. Design a repair/maintenance bay drainage system to capture all wash water, leaks and spills. Connect drains to a sump for collection and disposal. Direct connection of the repair/maintenance bays to the storm drain system is prohibited. If required by local jurisdiction, obtain an Industrial Waste Discharge Permit.

8.c. Other features which are comparable and equally effective. 9. Vehicle Wash Areas Priority projects that include areas for washing/steam cleaning of

vehicles shall use the following.

9.a. Self-contained; or covered with a roof or overhang. 9.b. Equipped with a clarifier or other pretreatment facility. 9.c. Properly connected to a sanitary sewer. 9.d. Other features which are comparable and equally effective.

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BMP YES NO N/A10. Outdoor Processing Areas Outdoor process equipment operations, such as rock grinding or

crushing, painting or coating, grinding or sanding, degreasing or parts cleaning, waste piles, and wastewater and solid waste treatment and disposal, and other operations determined to be a potential threat to water quality by the County shall adhere to the following requirements.

10.a. Cover or enclose areas that would be the most significant source of pollutants; or, slope the area toward a dead-end sump; or, discharge to the sanitary sewer system following appropriate treatment in accordance with conditions established by the applicable sewer agency.

10.b. Grade or berm area to prevent run-on from surrounding areas. 10.c. Installation of storm drains in areas of equipment repair is

prohibited.

10.d. Other features which are comparable or equally effective. 11. Equipment Wash Areas Outdoor equipment/accessory washing and steam cleaning activities

shall be.

11.a. Be self-contained; or covered with a roof or overhang. 11.b. Be equipped with a clarifier, grease trap or other pretreatment

facility, as appropriate

11.c. Be properly connected to a sanitary sewer. 11.d. Other features which are comparable or equally effective. 12. Parking Areas The following design concepts shall be considered, and incorporated

and implemented where determined applicable and feasible by the County.

12.a. Where landscaping is proposed in parking areas, incorporate landscape areas into the drainage design.

12.b. Overflow parking (parking stalls provided in excess of the County’s minimum parking requirements) may be constructed with permeable paving.

12.c. Other design concepts that are comparable and equally effective. 13. Fueling Area Non-retail fuel dispensing areas shall contain the following. 13.a. Overhanging roof structure or canopy. The cover’s minimum

dimensions must be equal to or greater than the area within the grade break. The cover must not drain onto the fuel dispensing area and the downspouts must be routed to prevent drainage across the fueling area. The fueling area shall drain to the project’s treatment control BMP(s) prior to discharging to the storm water conveyance system.

13.b. Paved with Portland cement concrete (or equivalent smooth impervious surface). The use of asphalt concrete shall be prohibited.

13.c. Have an appropriate slope to prevent ponding, and must be separated from the rest of the site by a grade break that prevents run-on of urban runoff.

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BMP YES NO N/A 13.d. At a minimum, the concrete fuel dispensing area must extend

6.5 feet (2.0 meters) from the corner of each fuel dispenser, or the length at which the hose and nozzle assembly may be operated plus 1 foot (0.3 meter), whichever is less.

Please list other project specific Source Control BMPs in the following box. Write N/A if there are none.

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TREATMENT CONTROL To select a structural treatment BMP using Treatment Control BMP Selection Matrix (Table 10), each priority project shall compare the list of pollutants for which the downstream receiving waters are impaired (if any), with the pollutants anticipated to be generated by the project (as identified in Table 4). Any pollutants identified by Table 4, which are also causing a Clean Water Act section 303(d) impairment of the receiving waters of the project, shall be considered primary pollutants of concern. Priority projects that are anticipated to generate a primary pollutant of concern shall select a single or combination of stormwater BMPs from Table 10, which maximizes pollutant removal for the particular primary pollutant(s) of concern. Priority development projects that are not anticipated to generate a pollutant for which the receiving water is CWA 303(d) impaired shall select a single or combination of stormwater BMPs from Table 10, which are effective for pollutant removal of the identified secondary pollutants of concern, consistent with the “maximum extent practicable” standard. Table 10. Treatment Control BMP Selection Matrix Pollutants of Concern

Bioretention Facilities (LID)*

Settling Basins

(Dry Ponds)

Wet Ponds and

Wetlands

Infiltration Facilities or

Practices (LID)*

Media Filters

High-rate biofilters

High-rate media filters

Trash Racks & Hydro -dynamic Devices

Coarse Sediment and Trash

High High High High High High High High

Pollutants that tend to associate with fine particles during treatment

High High High High High Medium Medium Low

Pollutants that tend to be dissolved following treatment

Medium Low Medium High Low Low Low Low

*Additional information is available in the County of San Diego LID Handbook.

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NOTES ON POLLUTANTS OF CONCERN: In Table 11, Pollutants of Concern are grouped as gross pollutants, pollutants that tend to associate with fine particles, and pollutants that remain dissolved. Table 11 Pollutant Coarse Sediment and

Trash Pollutants that tend to

associate with fine particles during

treatment

Pollutants that tend to be dissolved following

treatment

Sediment X X Nutrients X X Heavy Metals X Organic Compounds X Trash & Debris X Oxygen Demanding X Bacteria X Oil & Grease X Pesticides X A Treatment BMP must address runoff from developed areas. Please provide the post-construction water quality treatment volume or flow values for the selected project Treatment BMP(s). Guidelines for design calculations are located in Chapter 5, Section 4.3, Principle 8 of the County SUSMP. Label outfalls on the BMP map. The Water Quality peak rate of discharge flow (QWQ) and the Water Quality storage volume (VWQ) is dependent on the type of treatment BMP selected for the project.

Outfall Tributary Area (acres)

QWQ (cfs)

VWQ (ft3)

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Please check the box(s) that best describes the Treatment BMP(s) selected for this project. Biofilters

Bioretention swale Vegetated filter strip Stormwater Planter Box (open-bottomed) Stormwater Flow-Through Planter (sealed bottom) Bioretention Area Vegetated Roofs/Modules/Walls

Detention Basins Extended/dry detention basin with grass/vegetated

lining Extended/dry detention basin with impervious lining

Infiltration Basins Infiltration basin Infiltration trench Dry well Permeable Paving Gravel Permeable asphalt Pervious concrete Unit pavers, ungrouted, set on sand or gravel Subsurface reservoir bed

Wet Ponds or Wetlands Wet pond/basin (permanent pool) Constructed wetland

Filtration Media filtration Sand filtration

Hydrodynamic Separator Systems Swirl Concentrator Cyclone Separator

Trash Racks and Screens Include Treatment Datasheet as Attachment E. The datasheet should include the following:

COMPLETED NO

1. Description of how treatment BMP was designed. Provide a description for each type of treatment BMP.

2. Engineering calculations for the BMP(s)

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Please describe why the selected treatment BMP(s) was selected for this project. For projects utilizing a low performing BMP, please provide a detailed explanation.

MAINTENANCE Please check the box that best describes the maintenance mechanism(s) for this project. Guidelines for each category are located in Chapter 5, Section 5.2 of the County SUSMP.

SELECTED CATEGORY YES NO First Second1 Third1 Fourth

Note: 1. Projects in Category 2 or 3 may choose to establish or be included in a Stormwater Maintenance Assessment District for the long-term maintenance of treatment BMPs. ATTACHMENTS

Please include the following attachments. ATTACHMENT COMPLETED N/A

A Project Location Map B Site Map C Relevant Monitoring Data D LID and Treatment BMP Location Map E Treatment BMP Datasheets F Operation and Maintenance Program for

Treatment BMPs

G Fiscal Resources H Certification Sheet I Addendum Note: Attachments A and B may be combined.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA ATTACHMENT A: PROJECT LOCATION MAP Please see the attached map.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA ATTACHMENT B: PROJECT SITE MAP Please see the attached map.

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SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA ATTACHMENT C: RELEVANT MONITORING DATA There is no relevant monitoring data for the project site at this time.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA ATTACHMENT D: LID AND TREATMENT CONTROL BMP LOCATION MAP Please see the attached map.

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SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA ATTACHMENT E: TREATMENT BMP DATASHEETS Please see the attached references.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 1 -

ATTACHMENT E – VEGETATED SWALE CALCULATIONS The following calculations are meant to help determine the Q100 values for the various drainage aspects of this SWMP. Calculations have been taken by using data from the hydrology report and using CIVILCADD/CIVILDESIGN Software Version 7.7. Calculations are based on the following assumptions: Vegetated Swale Dimensions: n = 0.025 (per CASQA TC-30) Base Width = 0 feet Maximum Depth = 6” = 0.5 feet Side Slopes = 3:1 D-40 Rip Rap Energy Dissipator Dimensions: n = 0.037 (#2 Backing) Base Width = 2.5 feet Maximum Depth = 0.83 feet Side Slopes = 3 D-75 Brow Ditch Dimensions: n = 0.013 Base Width = 0 feet Maximum Depth = 12” = 1 foot Side Slopes = .8 Driveway Cross-Gutter Dimensions: n = 0.013 Base Width = 0 Maximum Depth = 0.05 feet Side Slopes = 1%

This space intentionally left blank

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 2 -

VEGETATED SWALE DATA SUMMARY

LENGTH (FT)

SWALE

LOCATION

DESIGN PER STD

WIDTH

(FT)

SLOPE

TIME (MIN)

DEPTH

(IN)

S1 165 100 3 2.5% 10.85 2.8 S2 175 100 3 1.2% 12.47 2.6 S3 135 100 3 1.0% 12.82 3.0 S4 145 100 3 0.9% 13.46 2.1 S5 130 100 3 0.5% 13.96 2.8 S6 135 100 3 2.1% 10.85 2.9 S7 175 100 3 1.2% 12.47 2.6 S8 100 100 3 1.3% 11.33 2.3

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 3 -

PARCEL 1 – PAD VEGETATED SWALES TO D-40 RIP RAP DISSIPATOR San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2006 Version 7.7 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 10/07/08 ------------------------------------------------------------------------ LAGUS MINOR SUBDIVISION TPM 20966 PARCEL 1 VEG SWALE CALCULATIONS WEI 04-187 RJR 10-7-08 ------------------------------------------------------------------------ ********* Hydrology Study Control Information ********** ------------------------------------------------------------------------ Program License Serial Number 6170 ------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0 English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 3.600 24 hour precipitation(inches) = 8.000 P6/P24 = 45.0% San Diego hydrology manual 'C' values used ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.110 to Point/Station 1.210 **** INITIAL AREA EVALUATION **** ______________________________________________________________________ Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Initial subarea total flow distance = 100.000(Ft.) Highest elevation = 1821.500(Ft.) Lowest elevation = 1819.000(Ft.) Elevation difference = 2.500(Ft.) Slope = 2.500 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 100.00 (Ft) for the top area slope value of 2.50 %, in a development type of 1.0 DU/A or Less In Accordance With Figure 3-3

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 4 -

Initial Area Time of Concentration = 10.34 minutes TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)] TC = [1.8*(1.1-0.3200)*( 100.000^.5)/( 2.500^(1/3)]= 10.34 Rainfall intensity (I) = 5.934(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.320 Subarea runoff = 0.306(CFS) Total initial stream area = 0.161(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.210 to Point/Station 1.420 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1819.000(Ft.) Downstream point elevation = 1817.400(Ft.) Channel length thru subarea = 65.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Estimated mean flow rate at midpoint of channel = 0.343(CFS) Manning's 'N' = 0.025 Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.343(CFS) Depth of flow = 0.231(Ft.), Average velocity = 2.137(Ft/s) Channel flow top width = 1.387(Ft.) Flow Velocity = 2.14(Ft/s) Travel time = 0.51 min. Time of concentration = 10.85 min. Critical depth = 0.240(Ft.) Adding area flow to channel Rainfall intensity (I) = 5.754(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Rainfall intensity = 5.754(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.320 CA = 0.064 Subarea runoff = 0.063(CFS) for 0.039(Ac.) Total runoff = 0.368(CFS) Total area = 0.200(Ac.) Depth of flow = 0.238(Ft.), Average velocity = 2.176(Ft/s) Critical depth = 0.248(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.110 to Point/Station 1.420 **** CONFLUENCE OF MINOR STREAMS **** ______________________________________________________________________ Along Main Stream number: 1 in normal stream number 1 Stream flow area = 0.200(Ac.)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 5 -

Runoff from this stream = 0.368(CFS) Time of concentration = 10.85 min. Rainfall intensity = 5.754(In/Hr) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.310 to Point/Station 1.410 **** INITIAL AREA EVALUATION **** ______________________________________________________________________ Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Initial subarea total flow distance = 100.000(Ft.) Highest elevation = 1819.500(Ft.) Lowest elevation = 1818.300(Ft.) Elevation difference = 1.200(Ft.) Slope = 1.200 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 70.00 (Ft) for the top area slope value of 1.20 %, in a development type of 1.0 DU/A or Less In Accordance With Figure 3-3 Initial Area Time of Concentration = 11.05 minutes TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)] TC = [1.8*(1.1-0.3200)*( 70.000^.5)/( 1.200^(1/3)]= 11.05 The initial area total distance of 100.00 (Ft.) entered leaves a remaining distance of 30.00 (Ft.) Using Figure 3-4, the travel time for this distance is 0.59 minutes for a distance of 30.00 (Ft.) and a slope of 1.20 % with an elevation difference of 0.36(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 0.588 Minutes Tt=[(11.9*0.0057^3)/( 0.36)]^.385= 0.59 Total initial area Ti = 11.05 minutes from Figure 3-3 formula plus 0.59 minutes from the Figure 3-4 formula = 11.64 minutes Rainfall intensity (I) = 5.499(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.320 Subarea runoff = 0.209(CFS) Total initial stream area = 0.119(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.410 to Point/Station 1.420 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1818.300(Ft.) Downstream point elevation = 1817.400(Ft.) Channel length thru subarea = 75.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 3.000

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 6 -

Slope or 'Z' of right channel bank = 3.000 Estimated mean flow rate at midpoint of channel = 0.255(CFS) Manning's 'N' = 0.025 Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.255(CFS) Depth of flow = 0.237(Ft.), Average velocity = 1.516(Ft/s) Channel flow top width = 1.421(Ft.) Flow Velocity = 1.52(Ft/s) Travel time = 0.82 min. Time of concentration = 12.47 min. Critical depth = 0.215(Ft.) Adding area flow to channel Rainfall intensity (I) = 5.262(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Rainfall intensity = 5.262(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.320 CA = 0.055 Subarea runoff = 0.079(CFS) for 0.052(Ac.) Total runoff = 0.288(CFS) Total area = 0.171(Ac.) Depth of flow = 0.248(Ft.), Average velocity = 1.563(Ft/s) Critical depth = 0.225(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.310 to Point/Station 1.420 **** CONFLUENCE OF MINOR STREAMS **** ______________________________________________________________________ Along Main Stream number: 1 in normal stream number 2 Stream flow area = 0.171(Ac.) Runoff from this stream = 0.288(CFS) Time of concentration = 12.47 min. Rainfall intensity = 5.262(In/Hr) Summary of stream data: Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr) 1 0.368 10.85 5.754 2 0.288 12.47 5.262 Qmax(1) = 1.000 * 1.000 * 0.368) + 1.000 * 0.870 * 0.288) + = 0.619 Qmax(2) = 0.914 * 1.000 * 0.368) + 1.000 * 1.000 * 0.288) + = 0.625

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 7 -

Total of 2 streams to confluence: Flow rates before confluence point: 0.368 0.288 Maximum flow rates at confluence using above data: 0.619 0.625 Area of streams before confluence: 0.200 0.171 Results of confluence: Total flow rate = 0.625(CFS) Time of concentration = 12.467 min. Effective stream area after confluence = 0.371(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.420 to Point/Station 1.430 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1817.400(Ft.) Downstream point elevation = 1815.500(Ft.) Channel length thru subarea = 10.000(Ft.) Channel base width = 2.500(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Manning's 'N' = 0.037 Maximum depth of channel = 0.830(Ft.) Flow(q) thru subarea = 0.625(CFS) Depth of flow = 0.077(Ft.), Average velocity = 2.980(Ft/s) Channel flow top width = 2.961(Ft.) Flow Velocity = 2.98(Ft/s) Travel time = 0.06 min. Time of concentration = 12.52 min. Critical depth = 0.119(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.110 to Point/Station 1.430 **** CONFLUENCE OF MAIN STREAMS **** ______________________________________________________________________ The following data inside Main Stream is listed: In Main Stream number: 1 Stream flow area = 0.371(Ac.) Runoff from this stream = 0.625(CFS) Time of concentration = 12.52 min. Rainfall intensity = 5.246(In/Hr) Summary of stream data: Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr) 1 0.625 12.52 5.246 Qmax(1) = 1.000 * 1.000 * 0.625) + = 0.625

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 8 -

Total of 1 main streams to confluence: Flow rates before confluence point: 0.625 Maximum flow rates at confluence using above data: 0.625 Area of streams before confluence: 0.371 Results of confluence: Total flow rate = 0.625(CFS) Time of concentration = 12.523 min. Effective stream area after confluence = 0.371(Ac.) End of computations, total study area = 0.371 (Ac.)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 9 -

PARCEL 2 – PAD VEGETATED SWALES TO D-40 RIP RAP DISSIPATOR TO D-75 DITCH TO D-40 RIP RAP DISSIPATOR San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2006 Version 7.7 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 10/07/08 ------------------------------------------------------------------------ LAGUS MINOR SUBDIVISION TPM 20966 PARCEL 2 PAD VEG SWALE CALCULATIONS WEI 04-187 RJR 10-7-08

------------------------------------------------------------------------ ********* Hydrology Study Control Information ********** ------------------------------------------------------------------------ Program License Serial Number 6170 ------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0 English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 3.600 24 hour precipitation(inches) = 8.000 P6/P24 = 45.0% San Diego hydrology manual 'C' values used ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.110 to Point/Station 1.210 **** INITIAL AREA EVALUATION **** ______________________________________________________________________ Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Initial subarea total flow distance = 100.000(Ft.) Highest elevation = 1803.500(Ft.) Lowest elevation = 1802.500(Ft.) Elevation difference = 1.000(Ft.) Slope = 1.000 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 70.00 (Ft) for the top area slope value of 1.00 %, in a development type of 1.0 DU/A or Less

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 10 -

In Accordance With Figure 3-3 Initial Area Time of Concentration = 11.75 minutes TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)] TC = [1.8*(1.1-0.3200)*( 70.000^.5)/( 1.000^(1/3)]= 11.75 The initial area total distance of 100.00 (Ft.) entered leaves a remaining distance of 30.00 (Ft.) Using Figure 3-4, the travel time for this distance is 0.63 minutes for a distance of 30.00 (Ft.) and a slope of 1.00 % with an elevation difference of 0.30(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 0.631 Minutes Tt=[(11.9*0.0057^3)/( 0.30)]^.385= 0.63 Total initial area Ti = 11.75 minutes from Figure 3-3 formula plus 0.63 minutes from the Figure 3-4 formula = 12.38 minutes Rainfall intensity (I) = 5.286(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.320 Subarea runoff = 0.230(CFS) Total initial stream area = 0.136(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.210 to Point/Station 1.420 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1802.500(Ft.) Downstream point elevation = 1802.200(Ft.) Channel length thru subarea = 35.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Estimated mean flow rate at midpoint of channel = 0.249(CFS) Manning's 'N' = 0.025 Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.249(CFS) Depth of flow = 0.250(Ft.), Average velocity = 1.329(Ft/s) Channel flow top width = 1.501(Ft.) Flow Velocity = 1.33(Ft/s) Travel time = 0.44 min. Time of concentration = 12.82 min. Critical depth = 0.213(Ft.) Adding area flow to channel Rainfall intensity (I) = 5.168(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Rainfall intensity = 5.168(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.320 CA = 0.051 Subarea runoff = 0.033(CFS) for 0.023(Ac.)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 11 -

Total runoff = 0.263(CFS) Total area = 0.159(Ac.) Depth of flow = 0.255(Ft.), Average velocity = 1.346(Ft/s) Critical depth = 0.217(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.110 to Point/Station 1.420 **** CONFLUENCE OF MINOR STREAMS **** ______________________________________________________________________ Along Main Stream number: 1 in normal stream number 1 Stream flow area = 0.159(Ac.) Runoff from this stream = 0.263(CFS) Time of concentration = 12.82 min. Rainfall intensity = 5.168(In/Hr) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.310 to Point/Station 1.410 **** INITIAL AREA EVALUATION **** ______________________________________________________________________ Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Initial subarea total flow distance = 100.000(Ft.) Highest elevation = 1803.500(Ft.) Lowest elevation = 1802.600(Ft.) Elevation difference = 0.900(Ft.) Slope = 0.900 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 70.00 (Ft) for the top area slope value of 0.90 %, in a development type of 1.0 DU/A or Less In Accordance With Figure 3-3 Initial Area Time of Concentration = 12.17 minutes TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)] TC = [1.8*(1.1-0.3200)*( 70.000^.5)/( 0.900^(1/3)]= 12.17 The initial area total distance of 100.00 (Ft.) entered leaves a remaining distance of 30.00 (Ft.) Using Figure 3-4, the travel time for this distance is 0.66 minutes for a distance of 30.00 (Ft.) and a slope of 0.90 % with an elevation difference of 0.27(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 0.657 Minutes Tt=[(11.9*0.0057^3)/( 0.27)]^.385= 0.66 Total initial area Ti = 12.17 minutes from Figure 3-3 formula plus 0.66 minutes from the Figure 3-4 formula = 12.82 minutes Rainfall intensity (I) = 5.167(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.320 Subarea runoff = 0.136(CFS) Total initial stream area = 0.082(Ac.)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 12 -

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.410 to Point/Station 1.420 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1802.600(Ft.) Downstream point elevation = 1802.200(Ft.) Channel length thru subarea = 45.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Estimated mean flow rate at midpoint of channel = 0.148(CFS) Manning's 'N' = 0.025 Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.148(CFS) Depth of flow = 0.204(Ft.), Average velocity = 1.182(Ft/s) Channel flow top width = 1.226(Ft.) Flow Velocity = 1.18(Ft/s) Travel time = 0.63 min. Time of concentration = 13.46 min. Critical depth = 0.172(Ft.) Adding area flow to channel Rainfall intensity (I) = 5.008(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Rainfall intensity = 5.008(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.320 CA = 0.031 Subarea runoff = 0.020(CFS) for 0.015(Ac.) Total runoff = 0.155(CFS) Total area = 0.097(Ac.) Depth of flow = 0.208(Ft.), Average velocity = 1.197(Ft/s) Critical depth = 0.176(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.310 to Point/Station 1.420 **** CONFLUENCE OF MINOR STREAMS **** ______________________________________________________________________ Along Main Stream number: 1 in normal stream number 2 Stream flow area = 0.097(Ac.) Runoff from this stream = 0.155(CFS) Time of concentration = 13.46 min. Rainfall intensity = 5.008(In/Hr) Summary of stream data: Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 13 -

1 0.263 12.82 5.168 2 0.155 13.46 5.008 Qmax(1) = 1.000 * 1.000 * 0.263) + 1.000 * 0.952 * 0.155) + = 0.411 Qmax(2) = 0.969 * 1.000 * 0.263) + 1.000 * 1.000 * 0.155) + = 0.410 Total of 2 streams to confluence: Flow rates before confluence point: 0.263 0.155 Maximum flow rates at confluence using above data: 0.411 0.410 Area of streams before confluence: 0.159 0.097 Results of confluence: Total flow rate = 0.411(CFS) Time of concentration = 12.817 min. Effective stream area after confluence = 0.256(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.420 to Point/Station 1.430 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1802.200(Ft.) Downstream point elevation = 1800.000(Ft.) Channel length thru subarea = 10.000(Ft.) Channel base width = 2.500(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Manning's 'N' = 0.037 Maximum depth of channel = 0.830(Ft.) Flow(q) thru subarea = 0.411(CFS) Depth of flow = 0.057(Ft.), Average velocity = 2.678(Ft/s) Channel flow top width = 2.845(Ft.) Flow Velocity = 2.68(Ft/s) Travel time = 0.06 min. Time of concentration = 12.88 min. Critical depth = 0.091(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.430 to Point/Station 1.510 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1800.000(Ft.) Downstream point elevation = 1794.000(Ft.) Channel length thru subarea = 75.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 0.800

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 14 -

Slope or 'Z' of right channel bank = 0.800 Estimated mean flow rate at midpoint of channel = 0.438(CFS) Manning's 'N' = 0.013 Maximum depth of channel = 1.000(Ft.) Flow(q) thru subarea = 0.438(CFS) Depth of flow = 0.290(Ft.), Average velocity = 6.516(Ft/s) Channel flow top width = 0.464(Ft.) Flow Velocity = 6.52(Ft/s) Travel time = 0.19 min. Time of concentration = 13.07 min. Critical depth = 0.449(Ft.) Adding area flow to channel Rainfall intensity (I) = 5.103(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Rainfall intensity = 5.103(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.320 CA = 0.092 Subarea runoff = 0.061(CFS) for 0.033(Ac.) Total runoff = 0.472(CFS) Total area = 0.289(Ac.) Depth of flow = 0.298(Ft.), Average velocity = 6.641(Ft/s) Critical depth = 0.465(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.510 to Point/Station 1.520 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1794.000(Ft.) Downstream point elevation = 1792.000(Ft.) Channel length thru subarea = 10.000(Ft.) Channel base width = 2.500(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Manning's 'N' = 0.037 Maximum depth of channel = 0.830(Ft.) Flow(q) thru subarea = 0.472(CFS) Depth of flow = 0.064(Ft.), Average velocity = 2.734(Ft/s) Channel flow top width = 2.885(Ft.) Flow Velocity = 2.73(Ft/s) Travel time = 0.06 min. Time of concentration = 13.13 min. Critical depth = 0.100(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.110 to Point/Station 1.520 **** CONFLUENCE OF MAIN STREAMS ****

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 15 -

______________________________________________________________________ The following data inside Main Stream is listed: In Main Stream number: 1 Stream flow area = 0.289(Ac.) Runoff from this stream = 0.472(CFS) Time of concentration = 13.13 min. Rainfall intensity = 5.088(In/Hr) Summary of stream data: Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr) 1 0.472 13.13 5.088 Qmax(1) = 1.000 * 1.000 * 0.472) + = 0.472 Total of 1 main streams to confluence: Flow rates before confluence point: 0.472 Maximum flow rates at confluence using above data: 0.472 Area of streams before confluence: 0.289 Results of confluence: Total flow rate = 0.472(CFS) Time of concentration = 13.132 min. Effective stream area after confluence = 0.289(Ac.) End of computations, total study area = 0.289 (Ac.)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 16 -

PARCEL 2 – PAD VEGETATED SWALES AND DRIVEWAY TO PIPE INLET TO D-40 RIP RAP DISSIPATOR San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2006 Version 7.7 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 10/07/08

------------------------------------------------------------------------ LAGUS MINOR SUBDIVISION TPM 20966 PARCEL 2 PAD VEG SWALE CALCULATIONS WEI 04-187 RJR 10-7-08 ------------------------------------------------------------------------ ********* Hydrology Study Control Information ********** ------------------------------------------------------------------------ Program License Serial Number 6170 ------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0 English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 3.600 24 hour precipitation(inches) = 8.000 P6/P24 = 45.0% San Diego hydrology manual 'C' values used ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.110 to Point/Station 2.210 **** INITIAL AREA EVALUATION **** ______________________________________________________________________ Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Initial subarea total flow distance = 100.000(Ft.) Highest elevation = 1803.500(Ft.) Lowest elevation = 1803.000(Ft.) Elevation difference = 0.500(Ft.) Slope = 0.500 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 50.00 (Ft)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 17 -

for the top area slope value of 0.50 %, in a development type of 1.0 DU/A or Less In Accordance With Figure 3-3 Initial Area Time of Concentration = 12.51 minutes TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)] TC = [1.8*(1.1-0.3200)*( 50.000^.5)/( 0.500^(1/3)]= 12.51 The initial area total distance of 100.00 (Ft.) entered leaves a remaining distance of 50.00 (Ft.) Using Figure 3-4, the travel time for this distance is 1.22 minutes for a distance of 50.00 (Ft.) and a slope of 0.50 % with an elevation difference of 0.25(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 1.221 Minutes Tt=[(11.9*0.0095^3)/( 0.25)]^.385= 1.22 Total initial area Ti = 12.51 minutes from Figure 3-3 formula plus 1.22 minutes from the Figure 3-4 formula = 13.73 minutes Rainfall intensity (I) = 4.944(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.320 Subarea runoff = 0.207(CFS) Total initial stream area = 0.131(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.210 to Point/Station 2.220 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1803.000(Ft.) Downstream point elevation = 1802.200(Ft.) Channel length thru subarea = 30.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Estimated mean flow rate at midpoint of channel = 0.320(CFS) Manning's 'N' = 0.025 Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.320(CFS) Depth of flow = 0.222(Ft.), Average velocity = 2.165(Ft/s) Channel flow top width = 1.333(Ft.) Flow Velocity = 2.17(Ft/s) Travel time = 0.23 min. Time of concentration = 13.96 min. Critical depth = 0.234(Ft.) Adding area flow to channel Rainfall intensity (I) = 4.891(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Rainfall intensity = 4.891(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 18 -

(Q=KCIA) is C = 0.320 CA = 0.088 Subarea runoff = 0.222(CFS) for 0.143(Ac.) Total runoff = 0.429(CFS) Total area = 0.274(Ac.) Depth of flow = 0.248(Ft.), Average velocity = 2.329(Ft/s) Critical depth = 0.264(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.220 to Point/Station 2.230 **** PIPEFLOW TRAVEL TIME (User specified size) **** ______________________________________________________________________ Upstream point/station elevation = 1802.200(Ft.) Downstream point/station elevation = 1795.500(Ft.) Pipe length = 20.00(Ft.) Slope = 0.3350 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 0.429(CFS) Given pipe size = 6.00(In.) Calculated individual pipe flow = 0.429(CFS) Normal flow depth in pipe = 1.47(In.) Flow top width inside pipe = 5.16(In.) Critical Depth = 4.00(In.) Pipe flow velocity = 11.47(Ft/s) Travel time through pipe = 0.03 min. Time of concentration (TC) = 13.99 min. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.230 to Point/Station 2.240 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1795.500(Ft.) Downstream point elevation = 1792.500(Ft.) Channel length thru subarea = 10.000(Ft.) Channel base width = 2.500(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Manning's 'N' = 0.037 Maximum depth of channel = 0.830(Ft.) Flow(q) thru subarea = 0.429(CFS) Depth of flow = 0.054(Ft.), Average velocity = 2.999(Ft/s) Channel flow top width = 2.822(Ft.) Flow Velocity = 3.00(Ft/s) Travel time = 0.06 min. Time of concentration = 14.04 min. Critical depth = 0.094(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.110 to Point/Station 2.240 **** CONFLUENCE OF MAIN STREAMS **** ______________________________________________________________________ The following data inside Main Stream is listed: In Main Stream number: 1 Stream flow area = 0.274(Ac.) Runoff from this stream = 0.429(CFS)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 19 -

Time of concentration = 14.04 min. Rainfall intensity = 4.872(In/Hr) Summary of stream data: Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr) 1 0.429 14.04 4.872 Qmax(1) = 1.000 * 1.000 * 0.429) + = 0.429 Total of 1 main streams to confluence: Flow rates before confluence point: 0.429 Maximum flow rates at confluence using above data: 0.429 Area of streams before confluence: 0.274 Results of confluence: Total flow rate = 0.429(CFS) Time of concentration = 14.045 min. Effective stream area after confluence = 0.274(Ac.) End of computations, total study area = 0.274 (Ac.)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 20 -

PARCEL 3 – PARCEL 1 RUNOFF PLUS PARCEL 3 PAD VEGETATED SWALES San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2006 Version 7.7 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 10/07/08

------------------------------------------------------------------------ LAGUS MINOR SUBDIVISION TPM 20966 PARCEL 2 PAD VEG SWALE CALCULATIONS WEI 04-187 RJR 10-7-08 ------------------------------------------------------------------------ ********* Hydrology Study Control Information ********** ------------------------------------------------------------------------ Program License Serial Number 6170 ------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0 English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 3.600 24 hour precipitation(inches) = 8.000 P6/P24 = 45.0% San Diego hydrology manual 'C' values used ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.110 to Point/Station 1.210 **** INITIAL AREA EVALUATION **** ______________________________________________________________________ Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Initial subarea total flow distance = 100.000(Ft.) Highest elevation = 1821.500(Ft.) Lowest elevation = 1819.000(Ft.) Elevation difference = 2.500(Ft.) Slope = 2.500 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 100.00 (Ft) for the top area slope value of 2.50 %, in a development type of 1.0 DU/A or Less In Accordance With Figure 3-3 Initial Area Time of Concentration = 10.34 minutes TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 21 -

TC = [1.8*(1.1-0.3200)*( 100.000^.5)/( 2.500^(1/3)]= 10.34 Rainfall intensity (I) = 5.934(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.320 Subarea runoff = 0.306(CFS) Total initial stream area = 0.161(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.210 to Point/Station 1.420 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1819.000(Ft.) Downstream point elevation = 1817.400(Ft.) Channel length thru subarea = 65.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Estimated mean flow rate at midpoint of channel = 0.343(CFS) Manning's 'N' = 0.025 Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.343(CFS) Depth of flow = 0.231(Ft.), Average velocity = 2.137(Ft/s) Channel flow top width = 1.387(Ft.) Flow Velocity = 2.14(Ft/s) Travel time = 0.51 min. Time of concentration = 10.85 min. Critical depth = 0.240(Ft.) Adding area flow to channel Rainfall intensity (I) = 5.754(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Rainfall intensity = 5.754(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.320 CA = 0.064 Subarea runoff = 0.063(CFS) for 0.039(Ac.) Total runoff = 0.368(CFS) Total area = 0.200(Ac.) Depth of flow = 0.238(Ft.), Average velocity = 2.176(Ft/s) Critical depth = 0.248(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.110 to Point/Station 1.420 **** CONFLUENCE OF MINOR STREAMS **** ______________________________________________________________________ Along Main Stream number: 1 in normal stream number 1 Stream flow area = 0.200(Ac.) Runoff from this stream = 0.368(CFS) Time of concentration = 10.85 min. Rainfall intensity = 5.754(In/Hr)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 22 -

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.310 to Point/Station 1.410 **** INITIAL AREA EVALUATION **** ______________________________________________________________________ Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Initial subarea total flow distance = 100.000(Ft.) Highest elevation = 1819.500(Ft.) Lowest elevation = 1818.300(Ft.) Elevation difference = 1.200(Ft.) Slope = 1.200 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 70.00 (Ft) for the top area slope value of 1.20 %, in a development type of 1.0 DU/A or Less In Accordance With Figure 3-3 Initial Area Time of Concentration = 11.05 minutes TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)] TC = [1.8*(1.1-0.3200)*( 70.000^.5)/( 1.200^(1/3)]= 11.05 The initial area total distance of 100.00 (Ft.) entered leaves a remaining distance of 30.00 (Ft.) Using Figure 3-4, the travel time for this distance is 0.59 minutes for a distance of 30.00 (Ft.) and a slope of 1.20 % with an elevation difference of 0.36(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 0.588 Minutes Tt=[(11.9*0.0057^3)/( 0.36)]^.385= 0.59 Total initial area Ti = 11.05 minutes from Figure 3-3 formula plus 0.59 minutes from the Figure 3-4 formula = 11.64 minutes Rainfall intensity (I) = 5.499(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.320 Subarea runoff = 0.209(CFS) Total initial stream area = 0.119(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.410 to Point/Station 1.420 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1818.300(Ft.) Downstream point elevation = 1817.400(Ft.) Channel length thru subarea = 75.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Estimated mean flow rate at midpoint of channel = 0.255(CFS) Manning's 'N' = 0.025 Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.255(CFS) Depth of flow = 0.237(Ft.), Average velocity = 1.516(Ft/s)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 23 -

Channel flow top width = 1.421(Ft.) Flow Velocity = 1.52(Ft/s) Travel time = 0.82 min. Time of concentration = 12.47 min. Critical depth = 0.215(Ft.) Adding area flow to channel Rainfall intensity (I) = 5.262(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Rainfall intensity = 5.262(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.320 CA = 0.055 Subarea runoff = 0.079(CFS) for 0.052(Ac.) Total runoff = 0.288(CFS) Total area = 0.171(Ac.) Depth of flow = 0.248(Ft.), Average velocity = 1.563(Ft/s) Critical depth = 0.225(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.310 to Point/Station 1.420 **** CONFLUENCE OF MINOR STREAMS **** ______________________________________________________________________ Along Main Stream number: 1 in normal stream number 2 Stream flow area = 0.171(Ac.) Runoff from this stream = 0.288(CFS) Time of concentration = 12.47 min. Rainfall intensity = 5.262(In/Hr) Summary of stream data: Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr) 1 0.368 10.85 5.754 2 0.288 12.47 5.262 Qmax(1) = 1.000 * 1.000 * 0.368) + 1.000 * 0.870 * 0.288) + = 0.619 Qmax(2) = 0.914 * 1.000 * 0.368) + 1.000 * 1.000 * 0.288) + = 0.625 Total of 2 streams to confluence: Flow rates before confluence point: 0.368 0.288 Maximum flow rates at confluence using above data: 0.619 0.625 Area of streams before confluence: 0.200 0.171

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 24 -

Results of confluence: Total flow rate = 0.625(CFS) Time of concentration = 12.467 min. Effective stream area after confluence = 0.371(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.420 to Point/Station 1.430 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1817.400(Ft.) Downstream point elevation = 1815.500(Ft.) Channel length thru subarea = 10.000(Ft.) Channel base width = 2.500(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Manning's 'N' = 0.037 Maximum depth of channel = 0.830(Ft.) Flow(q) thru subarea = 0.625(CFS) Depth of flow = 0.077(Ft.), Average velocity = 2.980(Ft/s) Channel flow top width = 2.961(Ft.) Flow Velocity = 2.98(Ft/s) Travel time = 0.06 min. Time of concentration = 12.52 min. Critical depth = 0.119(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.430 to Point/Station 2.230 **** IRREGULAR CHANNEL FLOW TRAVEL TIME **** ______________________________________________________________________ Estimated mean flow rate at midpoint of channel = 0.847(CFS) Depth of flow = 0.076(Ft.), Average velocity = 3.337(Ft/s) ******* Irregular Channel Data *********** ----------------------------------------------------------------- Information entered for subchannel number 1 : Point number 'X' coordinate 'Y' coordinate 1 0.00 0.50 2 21.50 0.00 3 43.90 0.50 Manning's 'N' friction factor = 0.020 ----------------------------------------------------------------- Sub-Channel flow = 0.847(CFS) ' ' flow top width = 6.677(Ft.) ' ' velocity= 3.337(Ft/s) ' ' area = 0.254(Sq.Ft) ' ' Froude number = 3.015 Upstream point elevation = 1815.500(Ft.) Downstream point elevation = 1780.000(Ft.) Flow length = 225.000(Ft.) Travel time = 1.12 min. Time of concentration = 13.65 min. Depth of flow = 0.076(Ft.) Average velocity = 3.337(Ft/s) Total irregular channel flow = 0.847(CFS)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 25 -

Irregular channel normal depth above invert elev. = 0.076(Ft.) Average velocity of channel(s) = 3.337(Ft/s) Adding area flow to channel Rainfall intensity (I) = 4.963(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [UNDISTURBED NATURAL TERRAIN ] (Permanent Open Space ) Impervious value, Ai = 0.000 Sub-Area C Value = 0.250 Rainfall intensity = 4.963(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.288 CA = 0.198 Subarea runoff = 0.357(CFS) for 0.316(Ac.) Total runoff = 0.981(CFS) Total area = 0.687(Ac.) Depth of flow = 0.080(Ft.), Average velocity = 3.462(Ft/s) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.230 to Point/Station 2.320 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1780.000(Ft.) Downstream point elevation = 1767.000(Ft.) Channel length thru subarea = 85.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Estimated mean flow rate at midpoint of channel = 1.076(CFS) Manning's 'N' = 0.025 Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 1.076(CFS) Depth of flow = 0.252(Ft.), Average velocity = 5.642(Ft/s) Channel flow top width = 1.513(Ft.) Flow Velocity = 5.64(Ft/s) Travel time = 0.25 min. Time of concentration = 13.90 min. Critical depth = 0.381(Ft.) Adding area flow to channel Rainfall intensity (I) = 4.905(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Rainfall intensity = 4.905(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.293 CA = 0.240 Subarea runoff = 0.196(CFS) for 0.132(Ac.) Total runoff = 1.177(CFS) Total area = 0.819(Ac.)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 26 -

Depth of flow = 0.261(Ft.), Average velocity = 5.771(Ft/s) Critical depth = 0.395(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.110 to Point/Station 2.320 **** CONFLUENCE OF MINOR STREAMS **** ______________________________________________________________________ Along Main Stream number: 1 in normal stream number 1 Stream flow area = 0.819(Ac.) Runoff from this stream = 1.177(CFS) Time of concentration = 13.90 min. Rainfall intensity = 4.905(In/Hr) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.310 to Point/Station 2.320 **** INITIAL AREA EVALUATION **** ______________________________________________________________________ Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Initial subarea total flow distance = 100.000(Ft.) Highest elevation = 1768.300(Ft.) Lowest elevation = 1767.000(Ft.) Elevation difference = 1.300(Ft.) Slope = 1.300 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 70.00 (Ft) for the top area slope value of 1.30 %, in a development type of 1.0 DU/A or Less In Accordance With Figure 3-3 Initial Area Time of Concentration = 10.76 minutes TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)] TC = [1.8*(1.1-0.3200)*( 70.000^.5)/( 1.300^(1/3)]= 10.76 The initial area total distance of 100.00 (Ft.) entered leaves a remaining distance of 30.00 (Ft.) Using Figure 3-4, the travel time for this distance is 0.57 minutes for a distance of 30.00 (Ft.) and a slope of 1.30 % with an elevation difference of 0.39(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 0.570 Minutes Tt=[(11.9*0.0057^3)/( 0.39)]^.385= 0.57 Total initial area Ti = 10.76 minutes from Figure 3-3 formula plus 0.57 minutes from the Figure 3-4 formula = 11.33 minutes Rainfall intensity (I) = 5.595(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.320 Subarea runoff = 0.152(CFS) Total initial stream area = 0.085(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.310 to Point/Station 2.320

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 27 -

**** CONFLUENCE OF MINOR STREAMS **** ______________________________________________________________________ Along Main Stream number: 1 in normal stream number 2 Stream flow area = 0.085(Ac.) Runoff from this stream = 0.152(CFS) Time of concentration = 11.33 min. Rainfall intensity = 5.595(In/Hr) Summary of stream data: Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr) 1 1.177 13.90 4.905 2 0.152 11.33 5.595 Qmax(1) = 1.000 * 1.000 * 1.177) + 0.877 * 1.000 * 0.152) + = 1.311 Qmax(2) = 1.000 * 0.815 * 1.177) + 1.000 * 1.000 * 0.152) + = 1.112 Total of 2 streams to confluence: Flow rates before confluence point: 1.177 0.152 Maximum flow rates at confluence using above data: 1.311 1.112 Area of streams before confluence: 0.819 0.085 Results of confluence: Total flow rate = 1.311(CFS) Time of concentration = 13.898 min. Effective stream area after confluence = 0.904(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.320 to Point/Station 2.330 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1767.000(Ft.) Downstream point elevation = 1762.500(Ft.) Channel length thru subarea = 10.000(Ft.) Channel base width = 2.500(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Manning's 'N' = 0.037 Maximum depth of channel = 0.830(Ft.) Flow(q) thru subarea = 1.311(CFS) Depth of flow = 0.092(Ft.), Average velocity = 5.125(Ft/s) Channel flow top width = 3.053(Ft.) Flow Velocity = 5.12(Ft/s) Travel time = 0.03 min. Time of concentration = 13.93 min. Critical depth = 0.189(Ft.) End of computations, total study area = 0.904 (Ac.)

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 28 -

PARCEL 3 – DRIVEWAY TO D-75 DITCH TO CROSS-GUTTER TO RIP RAP ENERGY DISSIPATOR San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2006 Version 7.7 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 10/07/08

------------------------------------------------------------------------ LAGUS MINOR SUBDIVISION TPM 20966 PARCEL 2 PAD VEG SWALE CALCULATIONS WEI 04-187 RJR 10-7-08 ------------------------------------------------------------------------ ********* Hydrology Study Control Information ********** ------------------------------------------------------------------------ Program License Serial Number 6170 ------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0 English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 3.600 24 hour precipitation(inches) = 8.000 P6/P24 = 45.0% San Diego hydrology manual 'C' values used ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.110 to Point/Station 5.120 **** INITIAL AREA EVALUATION **** ______________________________________________________________________ Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [UNDISTURBED NATURAL TERRAIN ] (Permanent Open Space ) Impervious value, Ai = 0.000 Sub-Area C Value = 0.250 Initial subarea total flow distance = 100.000(Ft.) Highest elevation = 1803.000(Ft.) Lowest elevation = 1793.000(Ft.) Elevation difference = 10.000(Ft.) Slope = 10.000 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 100.00 (Ft) for the top area slope value of 10.00 %, in a development type of

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 29 -

Permanent Open Space In Accordance With Figure 3-3 Initial Area Time of Concentration = 7.10 minutes TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)] TC = [1.8*(1.1-0.2500)*( 100.000^.5)/( 10.000^(1/3)]= 7.10 Rainfall intensity (I) = 7.564(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.250 Subarea runoff = 0.463(CFS) Total initial stream area = 0.245(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.120 to Point/Station 5.130 **** IRREGULAR CHANNEL FLOW TRAVEL TIME **** ______________________________________________________________________ Estimated mean flow rate at midpoint of channel = 0.645(CFS) Depth of flow = 0.066(Ft.), Average velocity = 3.325(Ft/s) ******* Irregular Channel Data *********** ----------------------------------------------------------------- Information entered for subchannel number 1 : Point number 'X' coordinate 'Y' coordinate 1 0.00 0.50 2 21.50 0.00 3 43.90 0.50 Manning's 'N' friction factor = 0.020 ----------------------------------------------------------------- Sub-Channel flow = 0.645(CFS) ' ' flow top width = 5.836(Ft.) ' ' velocity= 3.325(Ft/s) ' ' area = 0.194(Sq.Ft) ' ' Froude number = 3.214 Upstream point elevation = 1793.000(Ft.) Downstream point elevation = 1778.000(Ft.) Flow length = 80.000(Ft.) Travel time = 0.40 min. Time of concentration = 7.50 min. Depth of flow = 0.066(Ft.) Average velocity = 3.325(Ft/s) Total irregular channel flow = 0.645(CFS) Irregular channel normal depth above invert elev. = 0.066(Ft.) Average velocity of channel(s) = 3.325(Ft/s) Adding area flow to channel Rainfall intensity (I) = 7.301(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [UNDISTURBED NATURAL TERRAIN ] (Permanent Open Space ) Impervious value, Ai = 0.000 Sub-Area C Value = 0.250 Rainfall intensity = 7.301(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 30 -

(Q=KCIA) is C = 0.250 CA = 0.109 Subarea runoff = 0.334(CFS) for 0.192(Ac.) Total runoff = 0.798(CFS) Total area = 0.437(Ac.) Depth of flow = 0.072(Ft.), Average velocity = 3.506(Ft/s) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.130 to Point/Station 5.140 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1778.000(Ft.) Downstream point elevation = 1770.000(Ft.) Channel length thru subarea = 80.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Estimated mean flow rate at midpoint of channel = 0.885(CFS) Manning's 'N' = 0.025 Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.885(CFS) Depth of flow = 0.254(Ft.), Average velocity = 4.582(Ft/s) Channel flow top width = 1.523(Ft.) Flow Velocity = 4.58(Ft/s) Travel time = 0.29 min. Time of concentration = 7.79 min. Critical depth = 0.352(Ft.) Adding area flow to channel Rainfall intensity (I) = 7.124(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Rainfall intensity = 7.124(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.263 CA = 0.140 Subarea runoff = 0.200(CFS) for 0.096(Ac.) Total runoff = 0.997(CFS) Total area = 0.533(Ac.) Depth of flow = 0.265(Ft.), Average velocity = 4.721(Ft/s) Critical depth = 0.369(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.140 to Point/Station 5.150 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1770.000(Ft.) Downstream point elevation = 1769.000(Ft.) Channel length thru subarea = 10.000(Ft.) Channel base width = 2.500(Ft.) Slope or 'Z' of left channel bank = 3.000

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 31 -

Slope or 'Z' of right channel bank = 3.000 Manning's 'N' = 0.037 Maximum depth of channel = 0.830(Ft.) Flow(q) thru subarea = 0.997(CFS) Depth of flow = 0.122(Ft.), Average velocity = 2.857(Ft/s) Channel flow top width = 3.231(Ft.) Flow Velocity = 2.86(Ft/s) Travel time = 0.06 min. Time of concentration = 7.85 min. Critical depth = 0.160(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.150 to Point/Station 5.160 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1769.000(Ft.) Downstream point elevation = 1760.000(Ft.) Channel length thru subarea = 75.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 0.800 Slope or 'Z' of right channel bank = 0.800 Manning's 'N' = 0.013 Maximum depth of channel = 1.000(Ft.) Flow(q) thru subarea = 0.997(CFS) Depth of flow = 0.366(Ft.), Average velocity = 9.321(Ft/s) Channel flow top width = 0.585(Ft.) Flow Velocity = 9.32(Ft/s) Travel time = 0.13 min. Time of concentration = 7.99 min. Critical depth = 0.625(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.160 to Point/Station 5.170 **** IRREGULAR CHANNEL FLOW TRAVEL TIME **** ______________________________________________________________________ Depth of flow = 0.062(Ft.), Average velocity = 5.453(Ft/s) !!Warning: Water is above left or right bank elevations ******* Irregular Channel Data *********** ----------------------------------------------------------------- Information entered for subchannel number 1 : Point number 'X' coordinate 'Y' coordinate 1 0.00 0.05 2 2.50 0.00 3 5.00 0.05 Manning's 'N' friction factor = 0.013 ----------------------------------------------------------------- Sub-Channel flow = 0.997(CFS) ' ' flow top width = 5.000(Ft.) ' ' velocity= 5.453(Ft/s) ' ' area = 0.183(Sq.Ft) ' ' Froude number = 5.025

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment E - 32 -

Upstream point elevation = 1760.000(Ft.) Downstream point elevation = 1757.000(Ft.) Flow length = 16.000(Ft.) Travel time = 0.05 min. Time of concentration = 8.03 min. Depth of flow = 0.062(Ft.) Average velocity = 5.453(Ft/s) Total irregular channel flow = 0.997(CFS) Irregular channel normal depth above invert elev. = 0.062(Ft.) Average velocity of channel(s) = 5.453(Ft/s) !!Warning: Water is above left or right bank elevations ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.180 to Point/Station 5.170 **** SUBAREA FLOW ADDITION **** ______________________________________________________________________ Rainfall intensity (I) = 6.985(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (1.0 DU/A or Less ) Impervious value, Ai = 0.100 Sub-Area C Value = 0.320 Time of concentration = 8.03 min. Rainfall intensity = 6.985(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.271 CA = 0.168 Subarea runoff = 0.175(CFS) for 0.087(Ac.) Total runoff = 1.172(CFS) Total area = 0.620(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.170 to Point/Station 5.190 **** IMPROVED CHANNEL TRAVEL TIME **** ______________________________________________________________________ Upstream point elevation = 1757.000(Ft.) Downstream point elevation = 1754.000(Ft.) Channel length thru subarea = 10.000(Ft.) Channel base width = 2.500(Ft.) Slope or 'Z' of left channel bank = 3.000 Slope or 'Z' of right channel bank = 3.000 Manning's 'N' = 0.037 Maximum depth of channel = 0.830(Ft.) Flow(q) thru subarea = 1.172(CFS) Depth of flow = 0.097(Ft.), Average velocity = 4.322(Ft/s) Channel flow top width = 3.083(Ft.) Flow Velocity = 4.32(Ft/s) Travel time = 0.04 min. Time of concentration = 8.07 min. Critical depth = 0.176(Ft.) End of computations, total study area = 0.620 (Ac.)

Vegetated Swale TC-30

Design Considerations

Tributary Area

Area Required

Slope

Water Availability

Targeted Constituents

SedimentNutrientsTrashMetalsBacteriaOil and Grease Organics

Legend (Removal Effectiveness)

Low High

Medium

DescriptionVegetated swales are open, shallow channels with vegetationcovering the side slopes and bottom that collect and slowlyconvey runoff flow to downstream discharge points. They aredesigned to treat runoff through filtering by the vegetation in thechannel, filtering through a subsoil matrix, and/or infiltrationinto the underlying soils. Swales can be natural or manmade.They trap particulate pollutants (suspended solids and tracemetals), promote infiltration, and reduce the flow velocity of stormwater runoff. Vegetated swales can serve as part of a stormwater drainage system and can replace curbs, gutters and storm sewer systems.

California Experience Caltrans constructed and monitored six vegetated swales insouthern California. These swales were generally effective inreducing the volume and mass of pollutants in runoff. Even inthe areas where the annual rainfall was only about 10 inches/yr,the vegetation did not require additional irrigation. One factorthat strongly affected performance was the presence of largenumbers of gophers at most of the sites. The gophers createdearthen mounds, destroyed vegetation, and generally reduced theeffectiveness of the controls for TSS reduction.

AdvantagesIf properly designed, vegetated, and operated, swales canserve as an aesthetic, potentially inexpensive urbandevelopment or roadway drainage conveyance measure with significant collateral water quality benefits.

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Roadside ditches should be regarded as significant potential swale/buffer strip sites and should be utilized for this purpose whenever possible.

LimitationsCan be difficult to avoid channelization.

May not be appropriate for industrial sites or locations where spills may occur

Grassed swales cannot treat a very large drainage area. Large areas may be divided andtreated using multiple swales.

A thick vegetative cover is needed for these practices to function properly.

They are impractical in areas with steep topography.

They are not effective and may even erode when flow velocities are high, if the grass cover is not properly maintained.

In some places, their use is restricted by law: many local municipalities require curb andgutter systems in residential areas.

Swales are mores susceptible to failure if not properly maintained than other treatmentBMPs.

Design and Sizing GuidelinesFlow rate based design determined by local requirements or sized so that 85% of the annualrunoff volume is discharged at less than the design rainfall intensity.

Swale should be designed so that the water level does not exceed 2/3rds the height of thegrass or 4 inches, which ever is less, at the design treatment rate.

Longitudinal slopes should not exceed 2.5%

Trapezoidal channels are normally recommended but other configurations, such as parabolic, can also provide substantial water quality improvement and may be easier to mowthan designs with sharp breaks in slope.

Swales constructed in cut are preferred, or in fill areas that are far enough from an adjacentslope to minimize the potential for gopher damage. Do not use side slopes constructed of fill, which are prone to structural damage by gophers and other burrowing animals.

A diverse selection of low growing, plants that thrive under the specific site, climatic, andwatering conditions should be specified. Vegetation whose growing season corresponds to the wet season are preferred. Drought tolerant vegetation should be considered especiallyfor swales that are not part of a regularly irrigated landscaped area.

The width of the swale should be determined using Manning�s Equation using a value of0.25 for Manning�s n.

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Construction/Inspection ConsiderationsInclude directions in the specifications for use of appropriate fertilizer and soil amendmentsbased on soil properties determined through testing and compared to the needs of thevegetation requirements.

Install swales at the time of the year when there is a reasonable chance of successfulestablishment without irrigation; however, it is recognized that rainfall in a given year maynot be sufficient and temporary irrigation may be used.

If sod tiles must be used, they should be placed so that there are no gaps between the tiles;stagger the ends of the tiles to prevent the formation of channels along the swale or strip.

Use a roller on the sod to ensure that no air pockets form between the sod and the soil.

Where seeds are used, erosion controls will be necessary to protect seeds for at least 75 days after the first rainfall of the season.

PerformanceThe literature suggests that vegetated swales represent a practical and potentially effectivetechnique for controlling urban runoff quality. While limited quantitative performance dataexists for vegetated swales, it is known that check dams, slight slopes, permeable soils, densegrass cover, increased contact time, and small storm events all contribute to successful pollutantremoval by the swale system. Factors decreasing the effectiveness of swales include compactedsoils, short runoff contact time, large storm events, frozen ground, short grass heights, steep slopes, and high runoff velocities and discharge rates.

Conventional vegetated swale designs have achieved mixed results in removing particulate pollutants. A study performed by the Nationwide Urban Runoff Program (NURP) monitoredthree grass swales in the Washington, D.C., area and found no significant improvement in urbanrunoff quality for the pollutants analyzed. However, the weak performance of these swales wasattributed to the high flow velocities in the swales, soil compaction, steep slopes, and short grassheight.

Another project in Durham, NC, monitored the performance of a carefully designed artificialswale that received runoff from a commercial parking lot. The project tracked 11 storms andconcluded that particulate concentrations of heavy metals (Cu, Pb, Zn, and Cd) were reduced byapproximately 50 percent. However, the swale proved largely ineffective for removing solublenutrients.

The effectiveness of vegetated swales can be enhanced by adding check dams at approximately17 meter (50 foot) increments along their length (See Figure 1). These dams maximize the retention time within the swale, decrease flow velocities, and promote particulate settling.Finally, the incorporation of vegetated filter strips parallel to the top of the channel banks canhelp to treat sheet flows entering the swale.

Only 9 studies have been conducted on all grassed channels designed for water quality (Table 1). The data suggest relatively high removal rates for some pollutants, but negative removals for some bacteria, and fair performance for phosphorus.

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TC-30 Vegetated Swale

Table 1 Grassed swale pollutant removal efficiency data

Removal Efficiencies (% Removal)

Study TSS TP TN NO3 Metals Bacteria Type

Caltrans 2002 77 8 67 66 83-90 -33 dry swales

Goldberg 1993 67.8 4.5 - 31.4 42�62 -100 grassed channel

Seattle Metro and Washington Department of Ecology 1992

60 45 - -25 2�16 -25 grassed channel

Seattle Metro and Washington Department of Ecology, 1992

83 29 - -25 46�73 -25 grassed channel

Wang et al., 1981 80 - - - 70�80 - dry swale

Dorman et al., 1989 98 18 - 45 37�81 - dry swale

Harper, 1988 87 83 84 80 88�90 - dry swale

Kercher et al., 1983 99 99 99 99 99 - dry swale

Harper, 1988. 81 17 40 52 37�69 - wet swale

Koon, 1995 67 39 - 9 -35 to 6 - wet swale

While it is difficult to distinguish between different designs based on the small amount of available data, grassed channels generally have poorer removal rates than wet and dry swales,although some swales appear to export soluble phosphorus (Harper, 1988; Koon, 1995). It is not clear why swales export bacteria. One explanation is that bacteria thrive in the warm swalesoils.

Siting CriteriaThe suitability of a swale at a site will depend on land use, size of the area serviced, soil type,slope, imperviousness of the contributing watershed, and dimensions and slope of the swalesystem (Schueler et al., 1992). In general, swales can be used to serve areas of less than 10 acres,with slopes no greater than 5 %. Use of natural topographic lows is encouraged and naturaldrainage courses should be regarded as significant local resources to be kept in use (Young et al., 1996).

Selection Criteria (NCTCOG, 1993) Comparable performance to wet basins

Limited to treating a few acres

Availability of water during dry periods to maintain vegetation

Sufficient available land area

Research in the Austin area indicates that vegetated controls are effective at removing pollutantseven when dormant. Therefore, irrigation is not required to maintain growth during dry periods, but may be necessary only to prevent the vegetation from dying.

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The topography of the site should permit the design of a channel with appropriate slope andcross-sectional area. Site topography may also dictate a need for additional structural controls.Recommendations for longitudinal slopes range between 2 and 6 percent. Flatter slopes can beused, if sufficient to provide adequate conveyance. Steep slopes increase flow velocity, decreasedetention time, and may require energy dissipating and grade check. Steep slopes also can bemanaged using a series of check dams to terrace the swale and reduce the slope to withinacceptable limits. The use of check dams with swales also promotes infiltration.

Additional Design GuidelinesMost of the design guidelines adopted for swale design specify a minimum hydraulic residencetime of 9 minutes. This criterion is based on the results of a single study conducted in Seattle,Washington (Seattle Metro and Washington Department of Ecology, 1992), and is not wellsupported. Analysis of the data collected in that study indicates that pollutant removal at aresidence time of 5 minutes was not significantly different, although there is more variability in that data. Therefore, additional research in the design criteria for swales is needed. Substantialpollutant removal has also been observed for vegetated controls designed solely for conveyance(Barrett et al, 1998); consequently, some flexibility in the design is warranted.

Many design guidelines recommend that grass be frequently mowed to maintain dense coveragenear the ground surface. Recent research (Colwell et al., 2000) has shown mowing frequency or grass height has little or no effect on pollutant removal.

Summary of Design Recommendations 1) The swale should have a length that provides a minimum hydraulic residence time of

at least 10 minutes. The maximum bottom width should not exceed 10 feet unless a dividing berm is provided. The depth of flow should not exceed 2/3rds the height of the grass at the peak of the water quality design storm intensity. The channel slopeshould not exceed 2.5%.

2) A design grass height of 6 inches is recommended.

3) Regardless of the recommended detention time, the swale should be not less than100 feet in length.

4) The width of the swale should be determined using Manning�s Equation, at the peakof the design storm, using a Manning�s n of 0.25.

5) The swale can be sized as both a treatment facility for the design storm and as aconveyance system to pass the peak hydraulic flows of the 100-year storm if it is located �on-line.� The side slopes should be no steeper than 3:1 (H:V).

6) Roadside ditches should be regarded as significant potential swale/buffer strip sitesand should be utilized for this purpose whenever possible. If flow is to be introducedthrough curb cuts, place pavement slightly above the elevation of the vegetated areas.Curb cuts should be at least 12 inches wide to prevent clogging.

7) Swales must be vegetated in order to provide adequate treatment of runoff. It is important to maximize water contact with vegetation and the soil surface. For general purposes, select fine, close-growing, water-resistant grasses. If possible,divert runoff (other than necessary irrigation) during the period of vegetation

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TC-30 Vegetated Swale

establishment. Where runoff diversion is not possible, cover graded and seededareas with suitable erosion control materials.

MaintenanceThe useful life of a vegetated swale system is directly proportional to its maintenance frequency.If properly designed and regularly maintained, vegetated swales can last indefinitely. Themaintenance objectives for vegetated swale systems include keeping up the hydraulic and removal efficiency of the channel and maintaining a dense, healthy grass cover.

Maintenance activities should include periodic mowing (with grass never cut shorter than the design flow depth), weed control, watering during drought conditions, reseeding of bare areas,and clearing of debris and blockages. Cuttings should be removed from the channel anddisposed in a local composting facility. Accumulated sediment should also be removedmanually to avoid concentrated flows in the swale. The application of fertilizers and pesticidesshould be minimal.

Another aspect of a good maintenance plan is repairing damaged areas within a channel. For example, if the channel develops ruts or holes, it should be repaired utilizing a suitable soil thatis properly tamped and seeded. The grass cover should be thick; if it is not, reseed as necessary.Any standing water removed during the maintenance operation must be disposed to a sanitarysewer at an approved discharge location. Residuals (e.g., silt, grass cuttings) must be disposed in accordance with local or State requirements. Maintenance of grassed swales mostly involvesmaintenance of the grass or wetland plant cover. Typical maintenance activities aresummarized below:

Inspect swales at least twice annually for erosion, damage to vegetation, and sediment anddebris accumulation preferably at the end of the wet season to schedule summermaintenance and before major fall runoff to be sure the swale is ready for winter. However,additional inspection after periods of heavy runoff is desirable. The swale should be checkedfor debris and litter, and areas of sediment accumulation.

Grass height and mowing frequency may not have a large impact on pollutant removal.Consequently, mowing may only be necessary once or twice a year for safety or aesthetics or to suppress weeds and woody vegetation.

Trash tends to accumulate in swale areas, particularly along highways. The need for litterremoval is determined through periodic inspection, but litter should always be removedprior to mowing.

Sediment accumulating near culverts and in channels should be removed when it builds up to 75 mm (3 in.) at any spot, or covers vegetation.

Regularly inspect swales for pools of standing water. Swales can become a nuisance due tomosquito breeding in standing water if obstructions develop (e.g. debris accumulation,invasive vegetation) and/or if proper drainage slopes are not implemented and maintained.

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CostConstruction CostLittle data is available to estimate the difference in cost between various swale designs. Onestudy (SWRPC, 1991) estimated the construction cost of grassed channels at approximately$0.25 per ft2. This price does not include design costs or contingencies. Brown and Schueler (1997) estimate these costs at approximately 32 percent of construction costs for moststormwater management practices. For swales, however, these costs would probably be significantly higher since the construction costs are so low compared with other practices. A more realistic estimate would be a total cost of approximately $0.50 per ft2, which comparesfavorably with other stormwater management practices.

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TC-30 Vegetated Swale

Maintenance Cost Caltrans (2002) estimated the expected annual maintenance cost for a swale with a tributaryarea of approximately 2 ha at approximately $2,700. Since almost all maintenance consists of mowing, the cost is fundamentally a function of the mowing frequency. Unit costs developed by SEWRPC are shown in Table 3. In many cases vegetated channels would be used to conveyrunoff and would require periodic mowing as well, so there may be little additional cost for the water quality component. Since essentially all the activities are related to vegetationmanagement, no special training is required for maintenance personnel.

References and Sources of Additional Information Barrett, Michael E., Walsh, Patrick M., Malina, Joseph F., Jr., Charbeneau, Randall J, 1998, �Performance of vegetative controls for treating highway runoff,� ASCE Journal ofEnvironmental Engineering, Vol. 124, No. 11, pp. 1121-1128.

Brown, W., and T. Schueler. 1997. The Economics of Stormwater BMPs in the Mid-AtlanticRegion. Prepared for the Chesapeake Research Consortium, Edgewater, MD, by the Center for Watershed Protection, Ellicott City, MD.

Center for Watershed Protection (CWP). 1996. Design of Stormwater Filtering Systems.Prepared for the Chesapeake Research Consortium, Solomons, MD, and USEPA Region V, Chicago, IL, by the Center for Watershed Protection, Ellicott City, MD.

Colwell, Shanti R., Horner, Richard R., and Booth, Derek B., 2000. Characterization of Performance Predictors and Evaluation of Mowing Practices in Biofiltration Swales. Reportto King County Land And Water Resources Division and others by Center for Urban WaterResources Management, Department of Civil and Environmental Engineering, University of Washington, Seattle, WA

Dorman, M.E., J. Hartigan, R.F. Steg, and T. Quasebarth. 1989. Retention, Detention and Overland Flow for Pollutant Removal From Highway Stormwater Runoff. Vol. 1. FHWA/RD89/202. Federal Highway Administration, Washington, DC.

Goldberg. 1993. Dayton Avenue Swale Biofiltration Study. Seattle Engineering Department,Seattle, WA.

Harper, H. 1988. Effects of Stormwater Management Systems on Groundwater Quality.Prepared for Florida Department of Environmental Regulation, Tallahassee, FL, byEnvironmental Research and Design, Inc., Orlando, FL.

Kercher, W.C., J.C. Landon, and R. Massarelli. 1983. Grassy swales prove cost-effective for water pollution control. Public Works, 16: 53�55.

Koon, J. 1995. Evaluation of Water Quality Ponds and Swales in the Issaquah/East Lake Sammamish Basins. King County Surface Water Management, Seattle, WA, and WashingtonDepartment of Ecology, Olympia, WA.

Metzger, M. E., D. F. Messer, C. L. Beitia, C. M. Myers, and V. L. Kramer. 2002. The Dark SideOf Stormwater Runoff Management: Disease Vectors Associated With Structural BMPs.Stormwater 3(2): 24-39.Oakland, P.H. 1983. An evaluation of stormwater pollutant removal

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through grassed swale treatment. In Proceedings of the International Symposium of UrbanHydrology, Hydraulics and Sediment Control, Lexington, KY. pp. 173�182.

Occoquan Watershed Monitoring Laboratory. 1983. Final Report: Metropolitan WashingtonUrban Runoff Project. Prepared for the Metropolitan Washington Council of Governments, Washington, DC, by the Occoquan Watershed Monitoring Laboratory, Manassas, VA.

Pitt, R., and J. McLean. 1986. Toronto Area Watershed Management Strategy Study: HumberRiver Pilot Watershed Project. Ontario Ministry of Environment, Toronto, ON.

Schueler, T. 1997. Comparative Pollutant Removal Capability of Urban BMPs: A reanalysis.Watershed Protection Techniques 2(2):379�383.

Seattle Metro and Washington Department of Ecology. 1992. Biofiltration Swale Performance: Recommendations and Design Considerations. Publication No. 657. Water Pollution Control Department, Seattle, WA.

Southeastern Wisconsin Regional Planning Commission (SWRPC). 1991. Costs of UrbanNonpoint Source Water Pollution Control Measures. Technical report no. 31. SoutheasternWisconsin Regional Planning Commission, Waukesha, WI.

U.S. EPA, 1999, Stormwater Fact Sheet: Vegetated Swales, Report # 832-F-99-006http://www.epa.gov/owm/mtb/vegswale.pdf, Office of Water, Washington DC.

Wang, T., D. Spyridakis, B. Mar, and R. Horner. 1981. Transport, Deposition and Control ofHeavy Metals in Highway Runoff. FHWA-WA-RD-39-10. University of Washington,Department of Civil Engineering, Seattle, WA.

Washington State Department of Transportation, 1995, Highway Runoff Manual, WashingtonState Department of Transportation, Olympia, Washington.

Welborn, C., and J. Veenhuis. 1987. Effects of Runoff Controls on the Quantity and Quality of Urban Runoff in Two Locations in Austin, TX. USGS Water Resources Investigations Report No. 87-4004. U.S. Geological Survey, Reston, VA.

Yousef, Y., M. Wanielista, H. Harper, D. Pearce, and R. Tolbert. 1985. Best Management Practices: Removal of Highway Contaminants By Roadside Swales. University of CentralFlorida and Florida Department of Transportation, Orlando, FL.

Yu, S., S. Barnes, and V. Gerde. 1993. Testing of Best Management Practices for ControllingHighway Runoff. FHWA/VA-93-R16. Virginia Transportation Research Council, Charlottesville, VA.

Information ResourcesMaryland Department of the Environment (MDE). 2000. Maryland Stormwater DesignManual. www.mde.state.md.us/environment/wma/stormwatermanual. Accessed May 22,2001.

Reeves, E. 1994. Performance and Condition of Biofilters in the Pacific Northwest. WatershedProtection Techniques 1(3):117�119.

January 2003 California Stormwater BMP Handbook 11 of 13 New Development and Redevelopment

www.cabmphandbooks.com

TC-30 Vegetated Swale

Seattle Metro and Washington Department of Ecology. 1992. Biofiltration Swale Performance.Recommendations and Design Considerations. Publication No. 657. Seattle Metro andWashington Department of Ecology, Olympia, WA.

USEPA 1993. Guidance Specifying Management Measures for Sources of Nonpoint Pollution inCoastal Waters. EPA-840-B-92-002. U.S. Environmental Protection Agency, Office of Water.Washington, DC.

Watershed Management Institute (WMI). 1997. Operation, Maintenance, and Management ofStormwater Management Systems. Prepared for U.S. Environmental Protection Agency, Officeof Water. Washington, DC, by the Watershed Management Institute, Ingleside, MD.

12 of 13 California Stormwater BMP Handbook January 2003 New Development and Redevelopment

www.cabmphandbooks.com

Vegetated Swale TC-30

January 2003 California Stormwater BMP Handbook 13 of 13 New Development and Redevelopment

www.cabmphandbooks.com

Vegetated Swale TC-30

January 2003 California Stormwater BMP Handbook 13 of 13 New Development and Redevelopment

www.cabmphandbooks.com

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Final - 36 - 12/31/2007

Fact Sheet 4. Vegetated Swale / Rock Swale

Vegetated / rock swales are vegetated or rock lined earthen channels that collect, convey, and filter site water runoff and remove pollutants. Swales are an alternative to lined channels and pipes; configuration and setting are unique to each site. CHARACTERISTICS

• If properly designed and maintained, swales can last for at least 50 years. • Can be used in all soil types, natural or amended. • When swales are not holding water, they appear as a typical landscaped area. • Water is filtered by vegetation/rocks and pollutants are removed by

infiltration into the subsurface of the soil. • Swales also serve to delay runoff peaks by reducing flow velocities.

APPLICATION

• Swales are most effective in removing coarse to medium sized sediments. • Parking lot medians, perimeters of impervious pavements. • Street and highway medians, edges (in lieu of curb and gutter, where appropriate). • In combination with constructed treatment systems or sand filters.

DESIGN

• Vegetation of each swale is unique to the setting, function, climate, geology, and character of each site and climatic condition.

• Can be designed with natural or amended soils, depending on the infiltration rate provided by the natural condition versus the rate needed to reduce surface runoff .

• Grass swales move water more quickly than vegetated swales. A grass swale is planted with salt grass; a vegetated swale is planted with bunch grass, shrubs or trees.

• Rocks, gravel, boulders, and/or cobbles help slow peak velocity, allow sedimentation, and add aesthetic value.

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Final - 37 - 12/31/2007

• Pollutant removal effectiveness can be maximized by increasing residence time of water in swale using weirs or check dams.

• Swales are often used as an alternative to curbs and gutters along roadways, but can also be used to convey stormwater flows in recreation areas and parking lots.

• Calculations should also be provided proving the swale capable of safely conveying the 100-year flow to the swale without flooding adjacent property or infrastructure.

• See County of San Diego Drainage Design Manual for design criteria. (section 5.5) http://www.sdcounty.ca.gov/dpw/docs/hydrologymanual.pdf

MAINTENANCE

• Swale maintenance includes mowing and removing clippings and litter. Vegetated swales may require additional maintenance of plants.

• Periodically remove sediment accumulation at top of bank, in swale bed, or behind check dams.

• Monitor for erosion and reseed grass or replace plants, erosion control netting and mulch as necessary. Fertilize and replace vegetation well in advance of rainy season to minimize water quality degradation.

• Regular inspections and maintenance is required during the establishment period. LIMITATIONS

• Only suitable for grades between 1% and 6%; when greater than 2.5% should be paired with weir or check dam.

• “Turf” swales will commonly require irrigation and may not meet State water conservation goals.

• Irrigated vegetation is not appropriate in certain sites. Xeriscape techniques, natural stone and rock linings should be used as an alternative to turf.

• Wider road corridors may be required to incorporate swales. • Contributing drainage areas should be sized to meet the stormwater management

objective given the amount of flow that will be produced. • When contributing flow could cause formation of low-flow channel, channel

dividers must be constructed to direct flow and prevent erosion. ECONOMICS

• Estimated grass swale construction cost per linear foot $4.50-$8.50 (from seed) to $15-20 (from sod), compare to $2 per inch of diameter underground pipe e.g., a 12” pipe would cost $24 per linear foot).

• $0.75 annual maintenance cost per linear foot REFERENCES

• CALTRANS – Storm Water Handbook (cabmphandbooks.com) • For additional information pertaining to Swales, see the works cited in the San

Diego County LID Literature Index.

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Fact Sheet 7. Bioretention Systems

Bioretention systems are essentially a surface and sub-surface water filtration system. In function they are similar to sand filters. Bioretention systems incorporate both plants and underlying filter soils for removal of contaminants. These facilities normally consist of a treatment train approach: filter strip, sand bed, ponding area, organic layer, planting soil, and plants. CHARACTERISICS

• Effective in removing sediments and attached pollutants by filtration through surface vegetation, ground cover and underlying filter media layer

• Delay runoff peaks by providing retention capacity and reducing flow velocities. • Vegetation increases aesthetic value while also enhancing filtration capacity and

helping to maintain the porosity of the filter media. • Can be constructed as either large or small scale devices, with native or amended

soils. • Small scale units are usually located in a residential planter box that filters

collected stormwater through the filter media and to an outlet. • Larger scale devices work on the same methodology, however are generally

located along the streetscapes and retarding basins over large open areas. • In addition, there are two main types of bioretention system: Non-conveyance

systems, which generally pond runoff volume, and Conveyance, which generally convey minor storm events along longitudinal channels. Such conveyance systems generally include an amended soil layer under the surface for additional storage and filtration

APPLICATION

• Effective in removing medium to fine size sediments and attached pollutants (such as nutrients, free oils/grease and metals), but typically have higher pollutant

Typical Bioretention cross section, Anatomy of a Rain Garden, n.d.

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Final - 43 - 12/31/2007

removal efficiencies for a wider range of contaminants due to enhanced filtration/biological processes associated with the surface vegetation.

• Best suited to small residential, commercial, and industrial developments with high percentages of impervious areas, including parking lots, high density residential housing, and roadways.

• Aesthetic benefits due to the surface vegetation make bioretention systems appealing for incorporation into streetscape and general landscape features.

DESIGN

• Provide a gentle slope for overland flow and adequate water storage. No water should be allowed to pond in the bioretention system for longer than 72 hours.

• Usually designed in conjunction with swales and other devices upstream so as to reduce filter clogging and provide water treatment (treatment train).

• Filter media employed is usually the plant growing material, which may comprise soil, sand and peat mixtures.

• “Planting box” type systems should be restricted to very small catchment areas. • A subdrain system should be included in urban areas along with associated

cleanout to facilitate maintenance. • For more precise design techniques, see: CASQA (2003, January) California

Stormwater BMP Handbook: New Development and Redevelopment MAINTENANCE

• Generally, only routine periodic maintenance typical of any landscaped area (mulching, plant replacement, pruning, weeding) is necessary.

• Regular inspections and maintenance are particularly important during the vegetation establishment period.

• Routine maintenance should include a biannual health evaluation of the trees and shrubs and subsequent removal of any dead or diseased vegetation.

• Other potential tasks include soil pH regulation, erosion repair at inflow points, mulch replenishment, unclogging the under-drain, and repairing overflow structures.

LIMITATIONS

• Adequate sunlight is required for vegetation growth. • The use of irrigation may not meet State water conservation goals. Appropriate

drought-tolerant plants should be considered. • Placement may be limited by the need for upstream pre-treatment so as to avoid

filter clogging (treatment train). • Contributing drainage area should be less than 1 acre for small-scale, on-lot

devices • Bioretention (a BMP with incidental infiltration) is not an appropriate BMP when:

o the seasonal high groundwater table is within 6 feet of the ground surface (US EPA 1999) o at locations where or where surrounding soil stratum is unstable

• exceptions to the 6 foot separation can be made when: o the BMP is designed with an under-drain and approved by a qualified licensed

professional, or when:

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Final - 44 - 12/31/2007

o written approval of a separation in the interval of 4-6 feet has been obtained by the Regional Water Quality Control Board and the Department of Environmental Health.

• Site must contain sufficient elevation relief so that subdrain system may discharge to receiving swale, curb or storm drain system.

ECONOMICS

• Construction cost estimates for a bioretention area are slightly greater than those for the required landscaping for a new development (EPA, 1999).

• The operation and maintenance costs for a bioretention facility will be comparable to those of typical landscaping required for a site. (CASQA, 2003)

• Maintenance costs are projected at 5-7% of the construction cost annually.

REFERENCES • California Stormwater Quality Association. (2003, January) California

Stormwater BMP Handbook: New Development and Redevelopment. • URS Australia Pty Ltd, (2004, May), Water Sensitive Urban Design: Technical

Guidelines for Western Sydney, Upper Parramatta River Catchment Trust. • US EPA (1999, September) BMP Fact Sheet 832-F-99-012.

http://www.epa.gov/owm/mtb/biortn.pdf • US EPA (1999, August) Preliminary Studies: Preliminary Data Summary of

Urban Stormwater Best Management Practices. EPA-821-R-99-012 Part D. • For additional information pertaining to Bioretention Systems, see the works cited

in the San Diego County LID Literature Index.

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Fact Sheet 18. Rural Swale Systems

Rural swale systems are a combination of street design elements that allow for surface drainage while simultaneously protecting the roadway edge, organizing parking, and allowing for driveway access and pedestrian circulation. Generally consist of street sheet flows being directed to a vegetated swale or gravel shoulder, curbs only at street corners, and culverts under driveways and street crossings CHARACTERISTICS

• Shoulder can be designed to accommodate parking or to serve as a linear swale, permitting infiltration of stormwater along its entire length.

• Runoff from the street is not concentrated, but dispersed along its entire length, and build-up of pollutants in the soil is minimized.

APPLICATION

• Differing systems can be applied depending on the local characteristics, needs and zoning standards.

DESIGN

• Concrete curb and gutter not required. • Ensure that culverts under intersections drain, to avoid standing water and

resulting septic condition. • For steeper slopes, roadside swales should be protected to minimize erosion. • Provide concrete curb at intersection radii to protect roadway edge and

landscape area from turning movements. • Crown street to direct runoff to shoulders. If drainage is provided on one side

only, then provide cross-slope towards swale. • Protect pavement edge with rigid header of steel, wood or a concrete band poured

flush with the street surface.

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Final - 69 - 12/31/2007

• If parking is not desired on the shoulder, no parking signs and striping can be used.

• Central medians can be used to divide traffic for safety or aesthetics. MAINTENANCE

• Surface systems require periodic maintenance and inspection. • Maintenance for surface systems is different than most urban Public

Works Departments currently practice, and employee retraining may be required. • Surface drainage systems are easier to monitor and clear than

underground systems, because problems, when they occur, are visible and on the surface. This eliminates the need for subsurface inspection or street excavation.

LIMITATIONS

• Design and scope is dependant upon local conditions and zoning standards. ECONOMICS

• Surface swales are less costly to install than underground pipe systems, but may have higher on-going maintenance costs.

REFERENCES

• City of Folsom, CA. • For additional information pertaining to Rural Swale Systems, see the works cited

in the San Diego County LID Literature Index.

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Final - 80 - 12/31/2007

Fact Sheet 24. LID Driveway, Sidewalk, and Bike Path Design CHARACTERISTICS Driveways, sidewalks and bike paths are another source of impervious coverage that can adversely affect water quality by the runoff generated from their surface. Several management opportunities and strategies are available to reduce this impact, including:

• Reducing sidewalks to one side of the street. • Utilize shared driveways to provide access to several homes. • Disconnect bike paths from streets. Bike paths separated from roadways

by vegetated strips reduce runoff and traffic hazards. • Utilizing pervious materials to infiltrate or increase time of concentration of

storm flows. • Reducing driveway and sidewalk width when possible. • Directing driveway and sidewalk runoff to adjacent vegetation to capture,

infiltrate, and treat runoff. • Installing a bioretention area or swale between the street and sidewalk and

grading runoff from the sidewalk to these areas. • Planting trees between the sidewalk and streets to capture and infiltrate runoff. • Installing grated infiltration systems in sidewalks and bike paths to receive runoff

as sheet flow. These can be installed to protect trees or can provide off-line stormwater management via a grate over an infiltration trench.

APPLICATION

• Residential Subdivisions, single family and multi-family homes. • Commercial Development • Public Parks

DESIGN

• Grade driveways, sidewalks, and bike paths at a two percent slope to direct runoff to an adjacent vegetated area.

• Pervious materials such as permeable pavers, permeable concrete or asphalt, gravel, or mulch can be utilized for sidewalk surfaces.

• In some cases, sidewalks and bike paths can be placed between rows of homes to increase access and decrease overall effective imperviousness.

• Grated infiltration systems should include removable grates to allow for maintenance, and must be capable of bearing the weight of pedestrians.

LIMITATIONS

• Ordinances may require sidewalks on both sides of the street. • Groundwater table must not be within 10 feet of the bottom of infiltration

trenches.

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MAINTENANCE CONSIDERATIONS • Maintenance necessary is related to the techniques applied (permeable materials,

bioretention, swales). • Vector breeding may occur in bioretention and swales if not properly designed

or maintained. ECONOMICS

• Costs are related to the number, type and size of the techniques applied. REFERENCES

• For additional information pertaining to LID Driveway, Sidewalk, and Bike Path Design see the works cited in the San Diego County LID Literature Index.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA ATTACHMENT F: OPERATIONS AND MAINTENANCE PLAN Operations & Maintenance of BMPs is essential for the success of any SUSMP. In order to perform proper O&M the Lagus Minor Subdivision (TPM 20966, ER 05-03-004) will be required to maintain and inspect their Post Construction BMPs for the life of the project. An inspection schedule and maintenance directions must be prepared for each Post Construction BMP that is install on the project site. INSTALLED POST CONSTRUCTION BMP DEVICES The project will utilize vegetated swales, storm drain inlet stenciling and rip rap energy dissipation devices. INSPECTION FORM The project may use the attached form to keep a record of inspection and maintenance activities. The County of San Diego will have the required length of time that records must be kept, but keep in mind that the County of San Diego or the Regional Water Quality Control Board can ask for inspection and maintenance records for up to five years from the time that they occur. The attached form is general and blank and is intended to be copied for use. VEGETATED SWALES The following is inspection and maintenance information for the vegetated swales: Routine Action: Height of Vegetation Maintenance Indicator: Height of vegetation exceeds 12” Field Measurements: Visual Inspection Inspection Frequency: - Once per Wet Season

- Once per Dry Season Maintenance Activity: Cut vegetation to 6” Additional: Remove any trees or woody vegetation

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA Routine Action: Assess Vegetative Cover Maintenance Indicator: Less than 70% vegetation coverage Field Measurements: - Visual Inspection - Record barren areas - File as a persistent problem Inspection Frequency: - Every May

- Late each Wet Season - Late each Dry Season

Maintenance Activity: - Reseed/re-vegetate barren areas by November - Scarify area to restored and replant to 2” height

- If this is required two (2) seasons in a row then an erosion blanket will need to be installed prior to the third reseeding/re-vegetation.

Routine Action: Inspect for Debris Accumulation Maintenance Indicator: Debris or litter present Field Measurement: Visual Inspection Inspection Frequency: Periodic Maintenance Activity: Remove debris and trash and dispose of properly Routine Action: Inspect for Accumulated Sediment Maintenance Indicator: - Sediment at or near vegetation height - Channeling of flow - Inhibited flow due to shallow slope Field Measurement: Visual Inspection Inspection Frequency: Annual Maintenance Activity: - Remove sediment - If flow is channeled, determine cause and correct

- If sediment is deep enough to change flow gradient then remove all sediment during the dry season (May) and re-vegetate. Notify the City Engineer to determine if re-grading is required.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA Routine Action: Inspect for Burrows Maintenance Indicator: Burrows, holes or mounds Field Measurement: Visual Inspection Inspection Frequency: - Annual - After vegetation trimming

Maintenance Activity: Backfill burrows where seepage, erosion or leakage occur

Routine Action: General Maintenance Inspection Maintenance Indicator: Any damaged aspects (side slopes, inlet) Field Measurement: Visual Inspection

Inspection Frequency: - Late each Wet Season - Late each Dry Season

Maintenance Activity: Take corrective action prior to wet season Routine Action: Inspect for Standing Water

Maintenance Indicator: Standing water for more than 72 hours Field Measurements: - Visual Inspection

- Random side slope measurements Inspection Frequency: - Annually

- 72 hours after a target storm event (0.75 inches)

Maintenance Activity: - Drain facility - Check and unclog clogged orifice(s) - Notify engineer, if immediate solution is not evident.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA Routine Action: Inspection for Trash and Debris

Maintenance Indicator: Debris/trash present Field Measurements: - Visual Observation Inspection Frequency: - During routine inspections

Maintenance Activity: Remove and dispose of trash and debris Routine Action: Inspection for Sediment Management and Characterization of Sediment for Removal

Maintenance Indicator: Sediment depth exceeds marker on staff gage

Field Measurements: - Measure depth at apparent maximum and minimum accumulation of sediment - Calculate average depth

Inspection Frequency: - Annually

Maintenance Activity: - Remove and properly dispose of sediment - Re-grade if necessary

Routine Action: Inspect for Burrows Maintenance Indicator: Burrows, holes or mounds Field Measurement: Visual Inspection Inspection Frequency: - Annual - After rock re-distributions

Maintenance Activity: Backfill burrows where seepage, erosion or leakage occurs and re-distribute rock

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA Routine Action: General Maintenance Inspection

Maintenance Indicator: - Inlet structures, outlet structures, side slopes, or other features damaged, significant erosion, emergence of trees or woody vegetation, graffiti or vandalism, fence damage, etc.

Field Measurements: - Visual Inspection Inspection Frequency: - Semi Annually

- Late wet season - Late dry season (monthly)

Maintenance Activity: - Take corrective action prior to wet season - Consult engineers if immediate solution is not

evident RIP RAP ENERGY DISSIPATOR The following is inspection and maintenance information for the Rip Rap Energy Dissipators: Routine Action: Vegetation Maintenance Indicator: Vegetation Present Field Measurements: Visual Inspection Inspection Frequency: - Once per Wet Season

- Once per Dry Season Maintenance Activity: Remove any vegetation Routine Action: Assess Rock Cover Maintenance Indicator: Less than 70% rock coverage Field Measurements: - Visual Inspection - Record barren areas - File as a persistent problem Inspection Frequency: - Every May

- Late each Wet Season - Late each Dry Season

Maintenance Activity: - Replace rock as needed to mitigate barren spots

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Routine Action: Inspect for Debris Accumulation Maintenance Indicator: Debris or litter present Field Measurement: Visual Inspection Inspection Frequency: Periodic Maintenance Activity: Remove debris and trash and dispose of properly Routine Action: Inspect for Accumulated Sediment Maintenance Indicator: - Sediment at or near rock height - Channeling of flow - Inhibited flow due to shallow slope Field Measurement: Visual Inspection Inspection Frequency: Annual Maintenance Activity: - Remove sediment - If flow is channeled, determine cause and correct

- If sediment is deep enough to change flow gradient then remove all sediment during the dry season (May) and re-distribute rock. Notify the Agency Engineer to determine if re-grading is required.

Routine Action: Inspect for Burrows Maintenance Indicator: Burrows, holes or mounds Field Measurement: Visual Inspection Inspection Frequency: - Annual - After rock re-distributions

Maintenance Activity: Backfill burrows where seepage, erosion or leakage occurs and re-distribute rock

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA Routine Action: Side Slope Inspection Maintenance Indicator: Any damaged side slopes Field Measurement: Visual Inspection

Inspection Frequency: - Late each Wet Season - Late each Dry Season

Maintenance Activity: Take corrective action prior to wet season to maintain proper side slopes

STORM DRAIN STENCILING The following is inspection and maintenance information for Storm Drain Stenciling: Routine Action: Stenciling Maintenance Indicator: Stenciling Damaged Field Measurements: Visual Inspection Inspection Frequency: - Once per Wet Season

- Once per Dry Season Maintenance Activity: Re-Stencil as necessary

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

BMP INSPECTION FORM

GENERAL INFORMATION

Project Name

City Contract No

Contractor

Inspector’s Name

Inspector’s Title

Signature

Date of Inspection

r Prior to forecast rain r After a rain event Inspection Type (Check Applicable)

r 24-hr intervals during extended rain r Other

Season (Check Applicable) r Rainy (Wet) r Non-Rainy (Dry)

Storm Start Date & Time: Storm Duration (hrs): Storm Data

Time elapsed since last storm (Circle Applicable Units)

Min. Hr. Days

Approximate Rainfall Amount (mm)

NOTES: _________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

INSPECTION REQUIREMENTS

Requirement Yes No N/A Corrective Action

Vegetated Swales

Is the height of vegetation less than 12”?

Is the vegetation coverage 70% or more?

Is there debris or litter present?

Is the channel sedimented?

Are there burrows, mounds, or holes present?

Is there any damage to the vegetated swales?

Rip Rap Energy Dissipator

Is there vegetation present?

Is the rock coverage 70% or more?

Is there debris or litter present?

Is the channel sedimented?

Are there burrows, mounds, or holes present?

Is there any damage to the rock slopes?

Storm Drain Stenciling

Are the stencils visible?

NOTES: _________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA ATTACHMENT G: FISCAL RESOURCES The property owner is aware that they will be required to maintain their selected post construction BMPs. The project’s BMPs are First Category BMPs per the County of San Diego SUSMP (3-24-08) and therefore require no funding; however, the property owner is aware that the following ‘Mechanisms to Assure Maintenance’ apply to all installed First Category BMPs:

1 Stormwater Ordinance Requirement: The WPO requires this ongoing maintenance. In the event that the mechanisms below prove ineffective, or in addition to enforcing those mechanisms, civil action, criminal action or administrative citation could also be pursued for violations of the ordinance.

2 Public Nuisance Abatement: Under the WPO failure to maintain a BMP

would constitute a public nuisance, which may be abated under the Uniform Public Nuisance Abatement Procedure. This provides an enforcement mechanism additional to the above, and would allow costs of maintenance to be billed to the owner, a lien placed on the property, and the tax collection process to be used.

FUNDING Per Chapter 5: Maintenance Requirements for Treatment BMPs from the County of San Diego SUSMP for Land Development and Public Improvement Projects (3-24-08) the funding for First Category BMPs is listed as ‘None Required.’ COSTS Per Appendix H of the County Standards the estimated annual costs for maintenance of vegetated swales is estimated at approximately $3,000.00. Future property owners will incur these costs.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA ATTACHMENT H: CERTIFICATION SHEET This Stormwater Management Plan has been prepared under the direction of the following Registered Civil Engineer. The Registered Civil Engineer attests to the technical information contained herein and the engineering data upon which recommendations, conclusions, and decisions are based.

---------------------------------------------------- ------------------------------ GARY WYNN DATE

REGISTERED CIVIL ENGINEER

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA ATTACHMENT I: SWMP ADDENDUM Please see the attached Storm Water Management Plan Addendum.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment I – Addendum - 1 -

ATTACHMENT I – SWMP ADDENDUM This Storm Water Management Plan Addendum consists of all the extra information that is required by the County of San Diego in their Storm Water Management Plan – Major form. 1.0 TABLE 3 – STORMWATER QUALITY DETERMINATION This section consists of provides the answers to the questions in the Table 3 of the County of San Diego Major SWMP form.

1. Describe the topography of the project area. The project site is located in the low mountains of the Pacific Coastal Ranges. The site occupies the northeast facing slope of a northwest flowing, elongated drainage.

2. Describe the local land use within the project area and adjacent areas. The

local land use consists of agricultural, undeveloped, and low density residential.

3. Evaluate the presence of dry weather flow. The site natural drainage patterns

based on topography precludes any dry weather flows.

4. Determine the receiving waters that may be affected by the project throughout all phases of development (i.e., construction, maintenance and operation). In general, the downstream receiving waters for the project is ‘Keys Creek’ per the Region 9 Basin Plan as Hydrologic Unit Basin Number 903.12.

5. For the project limits, list the 303(d) impaired receiving water bodies and their

constituents of concern. The project site’s receiving waters is not listed on the ‘Proposed 2006 CWA Section 303(d) List of Water Quality Limited Segments’ provided by the San Diego Regional Board. Please see the attached statement.

6. Determine if there are any High Risk Areas (which is defined by the presence

of municipal or domestic water supply reservoirs or groundwater percolation facilities) within the project limits. There are no ground water reservoirs or groundwater percolation facilities within the project limits or associated witht e project’s receiving waters.

7. Determine the Regional Board special requirements, including TMDLs,

effluent limits, etc. The project site’s receiving waters is not listed on the ‘Proposed 2006 CWA Section 303(d) List of Water Quality Limited Segments Being Addressed by USEPA Approved TMDLS’ provided by the San Diego Regional Board. Please see the attached statement.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA

Attachment I – Addendum - 2 -

8. Determine the general climate of the project area. Identify annual rainfall and rainfall intensity curves. The general climate for the project site is coastal desert. Rainfall information is determined in the project’s hydrology report. This is a separate document under the same County of San Diego project number.

9. If considering Treatment BMPs, determine the soil classification, permeability,

erodibility, and depth to groundwater. The soil classification has been determined to be ‘Soil Type B’ per the County of San Diego Hydrology Manual (2003 edition). Please see the attached reference.

10. Determine contaminated or hazardous soils within the project area. The

project site is not anticipated to have any contaminated or hazardous soils within the project area. At this time a soils report has not been performed for the project site.

2.0 LID TABLE 8 INFORMATION This section consists of provides the additional answer to questions in Table 8 of the County of San Diego Major SWMP.

1. Conserve Natural Areas. The project site will be preserving natural areas by clustering the development as noted on the maps. All surrounding areas will be kept undeveloped in their natural grove conditions.

2. Minimize Disturbances to Natural Drainages The project site’s natural

drainages have been determined and will be avoided as much as possible. In addition, the project site will be utilizing vegetated swales and rip rap energy dissipators where project runoff discharges the developed areas of the site. This will lessen the impacts and disturbances to the local drainage basin.

3. Minimize and Disconnect Impervious Surfaces The project site proposes

as little paved areas as possible to service the proposed lots. Paving is designed to the minimum width allowed by the County of San Diego. Roof runoff will be designed to drain to adjacent landscaping and into project site swales.

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Table 2-2. BENEFICIAL USES OF INLAND SURFACE WATERS

● Existing Beneficial Use 1 Waterbodies are listed multiple times if they cross hydrologic area or sub area boundaries.

+ Excepted from MUN (See Text) 2 Beneficial use designations apply to all tributaries to the indicated waterbody, if not listed separately.

Table 2-2 BENEFICIAL USES 2 - 30

BENEFICIAL USE

Inland Surface Waters 1, 2

Hydrologic Unit Basin Number

M U N

A G R

I N D

P R O C

G W R

F R S H

P O W

R E C 1

R E C 2

B I O L

W A R M

C O L D

W I L D

R A R E

S P W N

San Luis Rey River Watershed – continued

San Luis Rey River 3.12 + ● ● ● ● ● ● ● ●

Live Oak Creek 3.12 + ● ● ● ● ● ● ●

Keys Creek 3.12 + ● ● ● ● ● ●

Moosa Canyon 3.15 + ● ● ● ● ● ●

unnamed intermittent streams 3.16 + ● ● ● ● ● ●

Moosa Canyon 3.14 + ● ● ● ● ● ●

Moosa Canyon 3.13 + ● ● ● ● ● ●

Turner Lake 3.13 See Reservoirs & Lakes – Table 2-4

South Fork Moosa Canyon 3.13 + ● ● ● ● ● ●

Moosa Canyon 3.12 + ● ● ● ● ● ●

Gopher Canyon 3.12 + ● ● ● ● ● ●

South Fork Gopher Canyon 3.12 + ● ● ● ● ● ●

San Luis Rey River 3.11 + ● ● ● ● ● ● ●

Pilgrim Creek 3.11 + ● ● ● ● ● ● ● ● ●

Windmill Canyon 3.11 + ● ● ● ● ● ● ●

Tuley Canyon 3.11 + ● ● ● ● ● ●

Lawerence Canyon 3.11 + ● ● ● ● ● ●

Mouth of San Luis Rey River 3.11 See Coastal Waters – Table 2-3

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA PROPOSED 2006 CWA SECTION 303(d) LIST OF WATER QUALITY LIMITED SEGMENTS The project site receiving water is not listed on the ‘Proposed 2006 CWA Section 303(d) List of Water Quality Limited Segments.’ This list is lengthy and is not included in this report as reference since the project site is not listed on it.

SWMP – MAJOR LAGUS MINOR SUBDIVISION (TPM 20966, ER 05-03-004) COUNTY OF SAN DIEGO, VALLEY CENTER, CA PROPOSED 2006 CWA SECTION 303(d) LIST OF WATER QUALITY LIMITED SEGMENTS – USEPA APPROVED TMDL BEING ADDRESSED BY USEPA APPROVED TMDLS The project site receiving water is not listed on the ‘Proposed 2006 CWA Section 303(d) List of Water Quality Limited Segment – USEPA Approved TDML Being Addressed by USEPA Approved TMDLs.’ This list is lengthy and is not included in this report as reference since the project site is not listed on it.